Systems and methods for joint replacement

ABSTRACT

Systems and methods for joint replacement are provided. The systems and methods include a surgical orientation device, a reference sensor device, and at least one orthopedic fixture. The surgical orientation device, reference sensor device, and orthopedic fixtures can be used to locate the orientation of an axis in the body, to adjust an orientation of a cutting plane or planes along a bony surface, or otherwise to assist in an orthopedic procedure(s).

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/267737, filed Feb. 5, 2019, which is a continuation of U.S. patentapplication Ser. No. 15/716971, filed Sep. 27, 2017, which is acontinuation of U.S. patent application Ser. No. 15/052071, filed Feb.24, 2016, which is a continuation of U.S. patent application Ser. No.13/398712, filed Feb. 16, 2012, which is a continuation of U.S. patentapplication Ser. No. 13/115,065, filed May 24, 2011, the entire contentsof each is incorporated in its entirety by reference herein. U.S. patentapplication Ser. No. 13/115,065 is a continuation-in-part of U.S. patentapplication Ser. No. 12/509,388, filed Jul. 24, 2009, the entirecontents of which is incorporated in its entirety by reference herein,and is also a continuation-in-part of U.S. patent application Ser. No.13/011,815, filed Jan. 21, 2011, which claims benefit under 35 U.S.C. §119(e) to U.S. Provisional Patent Application No. 61/297,215, filed Jan.21, 2010, U.S. Provisional Patent Application No. 61/297,212, filed Jan.21, 2010, and U.S. Provisional Patent Application No. 61/369,390, filedJul. 30, 2010, each of which is incorporated in its entirety byreference herein.

BACKGROUND OF THE INVENTIONS Field of the Inventions

The present application is directed to systems and methods for jointreplacement, in particular to systems and methods for knee jointreplacement that utilize a surgical orientation device or devices.

Description of the Related Art

Joint replacement procedures, including knee joint replacementprocedures, are commonly used to replace a patient's joint with aprosthetic joint component or components. Such procedures often use asystem or systems of surgical tools and devices, including but notlimited to cutting guides (e.g. cutting blocks) and surgical guides, tomake surgical cuts along a portion or portions of the patient's bone(s).

Current systems and methods often use expensive, complex, bulky, and/ormassive computer navigation systems which require a computer orcomputers, as well as three dimensional imaging, to track a spatiallocation and/or movement of a surgical instrument or landmark in thehuman body. These systems are used generally to assist a user todetermine where in space a tool or landmark is located, and oftenrequire extensive training, cost, and room.

Where such complex and costly systems are not used, simple methods areused, such as “eyeballing” the alignment of rods with anatomicalfeatures, including leg bones. These simple methods are not sufficientlyaccurate to reliably align and place prosthetic implant components andthe bones to which such components are attached.

SUMMARY OF THE INVENTIONS

Accordingly, there is a lack of devices, systems and methods that can beused to accurately position components of prosthetic joints withoutoverly complicating the procedures, crowding the medical personnel,and/or burdening the physician or health-care facility with the greatcost of complex navigation systems.

Therefore, in accordance with at least one embodiment, a femoral jigassembly can comprise a distal guide assembly configured to bepositioned adjacent to distal condyles of a femur, a microblock assemblyreleasably attachable to the distal guide assembly, the microblockassembly comprising a microblock member and a translating memberconfigured to be moved relative the microblock member, and a cuttingblock assembly releasably attachable to the microblock assembly.

In accordance with another embodiment, a surgical orientation system cancomprise a surgical orientation device comprising a first portablehousing configured to be coupled with a knee bone by way of one or moreorthopedic fixtures, a first sensor located within the first housing,the first sensor configured to monitor the orientation of the housing ina coordinate system and to generate a signal corresponding to theorientation of the surgical orientation device relative to thecoordinate system, and a display module configured to display anindication of a change in one or more angle measurements relative to thecoordinate system based at least in part on the signal, and a referencedevice comprising, a second portable housing configured to connect to aknee bone by way of one or more orthopedic fixtures, and a second sensorlocated within the second housing, the second sensor configured tomonitor the orientation of the second housing relative to the coordinatesystem, the second sensor configured to generate orientation datacorresponding to the monitored orientation of the reference device. Thesurgical orientation system can further comprise an orthopedic fixtureconfigured to be connected to a knee bone and with the surgicalorientation device and reference sensor such that the surgicalorientation device and reference device are separately moveable relativeto each other, wherein at least one of the surgical orientation deviceand reference device is further configured to determine the spatiallocation of the mechanical axis of the leg.

In accordance with another embodiment, an orthopedic system can comprisea portable surgical orientation device having an associatedthree-dimensional coordinate reference system and an interactive userinterface configured to display one or more angle measurementscorresponding to an offset from a flexion-extension angle or avarus-valgus angle of a mechanical axis of a femur, the surgicalorientation device having a first sensor, a reference device having asecond sensor, wherein each of the first and second sensors have atleast one of a three-axis accelerometer and a three-axis gyroscope, atleast one of the first and second sensors being configured to monitor anorientation of the surgical orientation device in the three-dimensionalcoordinate reference system and to generate orientation datacorresponding to the monitored orientation of the surgical orientationdevice. The orthopedic system can further comprise a coupling device, aninterface support member, and a femoral jig assembly comprising amicroblock assembly and a cutting block assembly, the femoral jigassembly being releasably attachable to the orientation device via thecoupling device, the second sensor via the interface support member, anddistal condyles of a femur via the microblock assembly.

In accordance with another embodiment, an orthopedic system capable ofmonitoring orientation within a three-dimensional coordinate referencesystem can comprise a portable surgical orientation device having a userinterface configured to indicate angular displacement of a mechanicalaxis of a femur in an anterior-posterior plane or in a medial-lateralplane, the surgical orientation device having a first sensor, and areference device having a second sensor, wherein at least one of thefirst and second sensors comprises a three-axis accelerometer and athree-axis gyroscope, at least one of the first and second sensors beingconfigured to monitor the orientation of the surgical orientation devicein the three-dimensional coordinate reference system and to generateorientation data corresponding to the monitored orientation of thesurgical orientation device. The orthopedic system can further comprisea fixture comprising a first member configured to couple with thesurgical orientation device, a second member configured to couple withthe reference device, and a base member configured to be secured to aportion of a distal femur, wherein at least one of the first member andthe second member is movably coupled with the base member.

In accordance with another embodiment, an orthopedic system formonitoring orientation in a three-dimensional coordinate referencesystem can comprise a base member attachable to a proximal aspect of atibia, at least one adjustment device connected to and moveable relativeto the base member, and at least one probe for referencing a pluralityof anatomical landmarks, the anatomical landmarks referencing amechanical axis of the leg. The at least one adjustment device can bemoveable in at least one degree of freedom to orient a cutting guiderelative to a proximal feature of the tibia, such that the cutting guideis oriented at a selected angle relative to the mechanical axis. Theorthopedic system can further comprise a first orientation devicecomprising an interactive user interface configured to display one ormore angle measurements corresponding to an offset from a posteriorslope angle or a varus-valgus angle of the mechanical axis the firstorientation device having a first sensor, the first orientation devicebeing coupled to or integrally formed with the at least one adjustmentdevice, and a second orientation device having a second sensor, thesecond orientation device being coupled to or integrally formed with thebase member, wherein each of the first and second sensors have at leastone of a three-axis accelerometer and a three-axis gyroscope, at leastone of the first and second sensors being configured to monitororientation of the first orientation device in the three- dimensionalcoordinate reference system and to generate orientation datacorresponding to the monitored orientation of the first orientationdevice.

In accordance with another embodiment, an implant alignment device cancomprise an orthopedic fixture having a base configured to couple with adistal portion of a femur or a proximal portion of a tibia, a moveableportion configured to move relative to the base, and a guide memberconfigured to couple with the moveable portion, a reference devicecoupled to or integrally formed with the base or moveable portion of theorthopedic fixture, the reference device configured to sense changes inorientation of a long axis of the femur or tibia relative to a fixedreference frame, and a surgical orientation device coupled to orintegrally formed with the base or moveable portion of the orthopedicfixture to enable positioning of the guide member in a prescribedorientation relative to the proximal tibia or distal femur.

In accordance with another embodiment, an orientation system cancomprise an orthopedic positioning jig comprising a first member and asecond member that is movable in two degrees of freedom relative to thefirst member and that is constrained in one degree of freedom, a firstorientation device configured as a tilt meter coupled with the firstmember and a second orientation device configured as a tilt metercoupled with the second member, the first and second orientation devicesoperably coupled to indicate angular orientation of a natural orsurgically created anatomical feature.

In accordance with another embodiment, a method for performing totalknee arthroplasty on a knee joint of a patient can comprise preparing adistal portion of a femur for receiving a knee implant, comprisingplacing the knee joint in flexion and exposing the distal end of thefemur, coupling a first orthopedic fixture to a distal portion of thefemur, the first orthopedic fixture comprising a surgical orientationdevice, the surgical orientation device comprising an orientation sensorand an interactive user interface configured to display an indication ofa change in one or more angle measurements corresponding to aflexion-extension angle or a varus-valgus angle of a mechanical axis ofthe femur, the first orthopedic fixture further comprising a referencedevice, the reference device comprising a reference sensor. The methodcan further comprise monitoring the orientation of the reference sensorwhile swinging the leg to obtain information regarding the location ofthe mechanical axis of the leg, adjusting a varus/valgus andflexion/extension angle of a portion of the first orthopedic fixture bymonitoring the first surgical orientation device and moving thereference device relative to the surgical orientation device, attachinga cutting block to the first orthopedic fixture, the cutting block beingoriented relative the adjusted varus/valgus and flexion/extension angle,and resecting the distal end of the femur.

In accordance with another embodiment, a method for performing totalknee arthroplasty on a knee joint of a patient can comprise attaching abase member of an orthopedic fixture to a proximal aspect of a tibiasuch that movement of the tibia produces corresponding movement of thebase member, the orthopedic fixture comprising at least one membermoveable relative the base member, the moveable member comprising aprobe for referencing a plurality of anatomical landmarks, attaching aportable surgical orientation device to the moveable member, theportable surgical orientation device comprising an interactive userinterface, the surgical orientation device having a first sensor,attaching a reference device to the base member, the reference devicehaving a second sensor, moving the moveable member and probe to contactanatomical locations on the leg, directing the surgical orientationdevice to determine the spatial location or orientation of themechanical axis based on the anatomical locations, and moving themoveable member such that a cutting guide is oriented at a selectedangle relative to the mechanical axis.

In accordance with another embodiment, a method for resolving angularorientation can comprise coupling with a bone an orthopedic positioningjig comprising a first member and a second member that is movable in twodegrees of freedom and constrained in one degree of freedom, theorthopedic fixture having a cutting guide and a first orientation deviceconfigured as a tilt meter coupled with the first member and a secondorientation device configured as a tilt meter coupled with the secondmember, and moving the first member relative to the second member toindicate angular orientation of the cutting guide relative to an axis ofinterest.

In accordance with another embodiment, a method of preparing fororthopedic surgery can comprise determining the orientation of amechanical axis of a bone or joint, coupling an orthopedic orientationassembly with an extremity of a patient, the orientation assembly havinga positioning device, a reference device and a surgical orientationdevice coupled with the positioning device, and maintaining an alignmentbetween the reference sensor and the surgical orientation device whilemoving the surgical orientation device to collect data indicative oforientation.

In accordance with another embodiment, a method of determining ananatomical feature during a knee procedure can comprise coupling anorientation system with a distal aspect of a femur, the orientationsystem comprising a housing, an orientation sensor disposed within thehousing, and a user interface operably coupled with the orientationsensor, interacting with the user interface to begin an analysis ofpotential sources of error in the orientation system after coupling theorientation system to the distal femoral aspect, and moving theorientation system to collect data indicative of the anatomical featurerelevant to the knee procedure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a representation of a human leg, identifying the femoralhead, knee joint, femur, tibia, and ankle;

FIG. 2A shows an assembled view of a femoral preparation system thataccording to one embodiment of the present invention, including ananterior probe;

FIG. 2B shows an assembled view of the femoral preparation system shownin FIG. 2A, including a cutting block instead of the anterior probe;

FIG. 3 is a perspective view of a surgical orientation device that canbe used with the femoral preparation system of FIGS. 2A and 2B;

FIG. 4 is a back view of the surgical orientation device of FIG. 3;

FIG. 5 is a perspective view of the surgical orientation device of FIG.3;

FIG. 6 is a top view of the surgical orientation device of FIG. 3;

FIG. 7 is a bottom view of the surgical orientation device of FIG. 3;

FIG. 8 is a block diagram of an electrical system of the surgicalorientation device of FIG. 3;

FIG. 8A is a block diagram of an electrical system of an orthopedicpreparation system that includes a surgical orientation device and areference device such as that illustrated in FIGS. 15-16;

FIGS. 9-11 illustrate operation of accelerometers according toembodiments that can be used as sensors in the electrical system of FIG.8;

FIG. 12 is a perspective view of interior components of the surgicalorientation device of FIG. 3;

FIG. 13 is a perspective view of another embodiment of the surgicalorientation device that can be used with the femoral preparation systemof FIGS. 2A and 2B;

FIG. 14 is an exploded view of the first coupling device of the femoralpreparation system of FIGS. 2A and 2B;

FIG. 15 is a first exploded view of an embodiment of the referencedevice of the femoral preparation system of FIGS. 2A and 2B;

FIG. 16 is a second exploded view of an embodiment of the referencedevice of the femoral preparation system of FIGS. 2A and 2B;

FIG. 17 is an exploded view of the femoral jig assembly of the femoralpreparation system of FIGS. 2A and 2B;

FIG. 18 is a perspective view of the distal guide assembly of thefemoral jig assembly shown in FIG. 17;

FIG. 19 is an exploded view of the microblock assembly of the femoraljig assembly shown in FIG. 17;

FIG. 20 is a perspective view of the cutting block of the femoral jigassembly shown in FIG. 17;

FIG. 21 is a top perspective view of the distal guide assembly and thecutting block of the femoral jig assembly shown in FIG. 17;

FIG. 22 is a femur and a tibia of a leg shown in a flexion position witha small hole drilled in the intercondylar notch of the femur;

FIG. 23 is a perspective view of the femoral jig assembly shown in FIG.17 in an assembled fashion attached to a distal end portion of a femur;

FIG. 24 is a perspective view of the femoral jig assembly shown in FIG.17 in an assembled fashion including at least one pin;

FIG. 25 is a perspective view of the femoral preparation system of FIGS.2A and 2B being used during a stage of a femoral preparation methodaccording to one embodiment of the present invention;

FIG. 26 is a perspective view of the femoral preparation system of FIGS.2A and 2B being used during another stage of a femoral preparationmethod according to one embodiment of the present invention;

FIG. 27 is a perspective view of the femoral preparation system of FIGS.2A and 2B being used during yet another stage of the femoral preparationmethod;

FIG. 28 is a perspective view of the femoral preparation system of FIGS.2A and 2B being used during another stage of the femoral preparationmethod;

FIG. 29 is a perspective view of one embodiment of an optional alignmentrod of the femoral preparation system of FIGS. 2A and 2B;

FIG. 30 is a perspective view of another embodiment of an optionalalignment rod of the femoral preparation system of FIGS. 2A and 2B;

FIG. 31 is a perspective view of the femoral preparation system of FIGS.2A and 2B being used during yet another stage of the femoral preparationmethod;

FIGS. 31A-C are perspective views of an alternative embodiment of afemoral preparation system.

FIGS. 31D-F are perspective views of another alternative embodiment of afemoral preparation system.

FIGS. 32A-J show screen displays for a femoral preparation methodgenerated by one embodiment of the interactive user interface of thesurgical orientation device of FIG. 3;

FIG. 33 is an assembled view of a tibial preparation system according toone embodiment;

FIGS. 34-38 are assembled and exploded views of the tibial jig assemblyof the tibial preparation system of FIG. 33;

FIGS. 39A-B are perspective and exploded views of the mounting barassembly of the tibial jig assembly of FIG. 34;

FIGS. 40A-B are perspective and exploded views of the posterior slopeassembly of the tibial jig assembly of FIG. 34;

FIG. 41 is a perspective view of the distal tube assembly of the tibialpreparation system of FIG. 33;

FIG. 42 is a perspective view of the probe assembly of the tibialpreparation system of FIG. 33;

FIG. 43 is a perspective view of the stylus resection guide of thetibial preparation system of FIG. 33;

FIGS. 44A-B are exploded and perspective view of the tibial cuttingblock assembly of the tibial preparation system of FIG. 33;

FIGS. 45A-C are exploded and perspective views of a midline probeassembly of the tibial preparation system of FIG. 33;

FIG. 46 is a perspective view of the tibial preparation system of FIG.33 being used during a stage of a tibial preparation method according toone embodiment of the present invention;

FIG. 47 is a perspective view of the tibial preparation system of FIG.33 being used during another stage of a tibial preparation methodaccording to one embodiment;

FIG. 48 is a perspective view of the tibial preparation system of FIG.33 being used during another stage of a tibial preparation methodaccording to one embodiment of the present invention;

FIG. 49 is a perspective view of the tibial preparation system of FIG.33 being used during another stage of a tibial preparation methodaccording to one embodiment of the present invention;

FIG. 50 is a perspective view of the tibial preparation system of FIG.33 being used during another stage of a tibial preparation methodaccording to one embodiment of the present invention;

FIGS. 50A-B are perspective views of a variation of the tibialpreparation system of FIG. 33 that couples a proximal portion thereofwith a tibial plateau;

FIG. 50C is a schematic illustration showing calculations and operationsfor an embodiment of a method.

FIGS. 51A-L show screen displays for a tibial method generated by oneembodiment of the interactive user interface of the surgical orientationdevice of FIG. 3; and

FIGS. 52-55 show additional screen displays generated by one embodimentof the interactive user interface of the surgical orientation device ofFIG. 3.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Although certain preferred embodiments and examples are disclosed below,it will be understood by those skilled in the art that the inventivesubject matter extends beyond the specifically disclosed embodiments toother alternative embodiments and/or uses of the invention, and toobvious modifications and equivalents thereof. Thus it is intended thatthe scope of the inventions herein disclosed should not be limited bythe particular disclosed embodiments described herein. Thus, forexample, in any method or process disclosed herein, the acts oroperations making up the method/process may be performed in any suitablesequence, and are not necessarily limited to any particular disclosedsequence. For purposes of contrasting various embodiments with the priorart, certain aspects and advantages of these embodiments are describedwhere appropriate herein. Of course, it is to be understood that notnecessarily all such aspects or advantages may be achieved in accordancewith any particular embodiment. Thus, for example, it should berecognized that the various embodiments may be carried out in a mannerthat achieves or optimizes one advantage or group of advantages astaught herein without necessarily achieving other aspects or advantagesas may be taught or suggested herein.

In addition, in this description, a “module” includes, but is notlimited to, software or hardware components which perform certain tasks.Thus, a module may include object-oriented software components, classcomponents, procedures, subroutines, data structures, segments ofprogram code, drivers, firmware, microcode, circuitry, data, tables,arrays, etc. Those with ordinary skill in the art will also recognizethat a module can be implemented using a wide variety of differentsoftware and hardware techniques.

The following sections describe in detail systems and methods for atotal knee joint replacement procedure. The knee joint often requiresreplacement in the form of prosthetic components due to strain, stress,wear, deformation, misalignment, and/or other conditions in the joint.Prosthetic knee joint components are designed to replace a distalportion or portions of a femur and/or a proximal portion or portions ofa tibia.

FIG. 1 illustrates a femur F and tibia T, with the distal portion of thefemur F and proximal portion of the tibia T forming the knee joint. Toprovide the reader with the proper orientation of the instruments and toassist in more fully understanding the construction of the instruments,a small chart is included on FIG. 1 and FIG. 33. The charts indicate thegeneral directions--anterior, posterior, medial, and lateral, as well asproximal and distal. These terms relate to the orientation of the kneebones, such as the femur and tibia and will be used in the descriptionsof the various instruments consistent with their known medical usage.Additionally, the terms varus/valgus and posterior/anterior are usedherein to describe directional movement. Varus/valgus is a broad term asused herein, and includes, without limitation, rotational movement in amedial and/or lateral direction relative to the knee joint shown in FIG.1 (e.g. right and left in the page). Posterior/anterior is a broad termas used herein, and includes, without limitation, rotational movement ina posterior and/or anterior direction (e.g. in a flexion/extensiondirection, or into and out of the page) relative to the knee joint shownin FIG. 1.

Prior to replacing the knee joint with prosthetic components, surgicalcuts commonly called resections are generally made with a cutting toolor tools along a portion or portions of both the proximal tibia anddistal femur. These cuts are made to prepare the tibia and femur for theprosthetic components. After the cuts are made, the prostheticcomponents can be attached and/or secured to the tibia and femur.

The desired orientation and/or position of these cuts, and of theprosthetic components, can be determined pre-operatively and based, forexample, on a mechanical axis running through an individual patient'sleg. Once the desired locations of these cuts are determinedpre-operatively, the surgeon can use the systems and methods describedherein to make the cuts accurately. While the systems and methods aredescribed in the context of a knee joint replacement procedure, thesystems and/or their components and methods can similarly be used inother types of medical procedures, including but not limited to shoulderand hip replacement procedures.

I. Overview of Systems And Methods

FIGS. 2A, 2B, and 33 show various systems which can be used inorthopedic procedures, including but not limited to knee jointreplacement procedures. The systems can include a femoral preparationsystem 10, and a tibial preparation system 210. As described below, eachof these systems can be embodied in a number of variations withdifferent advantages.

II. Femoral Preparation Systems

With reference to FIGS. 2A and 2B, the femoral preparation system 10 canbe used to modify a natural femur with a distal femoral resection,enabling a prosthetic component to be securely mounted upon the distalend of the femur. The femoral preparation system 10 can comprise, forexample, a femoral jig assembly 12, a surgical orientation device 14, areference device 16, a first coupling device 18, and a second couplingdevice 20.

A. Surgical Orientation Devices & Systems

The surgical orientation device 14 can be used to measure and record thelocation of anatomical landmarks used in a total knee procedure, such asthe location of the mechanical axis of a leg (and femur). “Surgicalorientation device” is a broad term and is to be given its ordinary andcustomary meaning to a person of ordinary skill in the art (i.e. it isnot to be limited to a special or customized meaning) and includes,without limitation, any device that can be used to provide orientationinformation or perform orientation calculations for use in a surgical orother procedure. The mechanical axis of a leg, as defined herein,generally refers to an axial line extending from the center of rotationof a proximal head of a femur (e.g. the center of the femoral head)through, ideally, the approximate center of the knee, to a center, ormid-point, of the ankle (see, for example, FIG. 1). The mechanical axisof the femur is the same axial line extending from the center ofrotation of the proximal head of the femur through the center of thedistal end of the femur (the center of distal end of the femur iscommonly described as the center of the intercondylar notch). Generally,an ideal mechanical axis in a patient allows load to pass from thecenter of the hip, through the center of the knee, and to the center ofthe ankle. The surgical orientation device 14, in conjunction with thereference device 16 described herein, can be used to locate the spatialorientation of the mechanical axis. In certain techniques describedherein, the surgical orientation device 14 and the reference device 16can be used to locate one, two, or more planes intersecting themechanical axis. The surgical orientation device 14 and the referencedevice 16 can also be used for verifying an alignment of an orthopedicfixture or fixtures, or a cutting plane or planes, during an orthopedicprocedure. The surgical orientation device 14, and the reference device16, as described herein, can each be used alone or in conjunction withother devices, components, and/or systems.

Referring to FIG. 3, which shows an embodiment of the surgicalorientation device 14, the surgical orientation device 14 can comprise agenerally rectangular-shaped, box-like structure having an outer housing22. The outer housing 22 can be portable. The outer housing 22 can becomprised, at least in part, of plastic including but not limited toABS, polycarbonate, or other suitable material. The surgical orientationdevice 14 can be configured for hand-held use.

With continued reference to FIG. 3, a front side 24, or a portion of thefront side 24, of the surgical orientation device 14 can comprise adisplay 26. The display 26 can be a separate component from the outerhousing 22 or can be integrated on or within the outer housing 22. Thedisplay 26 can comprise an output device. For example, the display 26can comprise a liquid crystal display (“LCD”) or Ferroelectric LiquidCrystal on Silicon (“FLCOS”) display screen. The display screen can besized such that a user can readily read numbers, lettering, and/orsymbols displayed on the display screen while performing a medicalprocedure. In at least one embodiment, the display 26 can comprise aQuarter Video Graphics Array (“QVGA”) Thin Film Transistor (“TFT”) LCDscreen. Other types of display screens can also be used, as can othershapes, sizes, and locations for the display 26 on the surgicalorientation device 14.

The surgical orientation device 14 can further comprise at least oneuser input device 28. The at least one user input device 28 can comprisea plurality of buttons located adjacent the display 26. The buttons canbe activated, for example, by a finger, hand, and/or instrument toselect a mode or modes of operation of the surgical orientation device14, as discussed further below. In a preferred arrangement, the at leastone user input device 28 can comprise three buttons located underneaththe display 26 as illustrated in FIG. 3. In other embodiments, the userinput device 28 can be a separate component from the housing 22. Forexample, the user input device 28 can comprise a remote input devicecoupled to the surgical orientation device 14 via a wired or wirelessconnection. In yet other embodiments, the user input device 28 cancomprise a microphone operating in conjunction with a speech recognitionmodule configured to receive and process verbal instructions from auser.

As discussed further herein, the surgical orientation device 14 caninclude a user interface with which a user can interact during aprocedure. In one embodiment, the display 26 and at least one user inputdevice 28 can form a user interface. The user interface can allow asurgeon, medical personnel, and/or other user to operate the surgicalorientation device 14 with ease, efficiency, and accuracy. Specificexamples and illustrations of how the user interface can operate inconjunction with specific methods are disclosed further herein.

FIGS. 4 and 5 show a back side 30 of the surgical orientation device 14.The back side 30 can include an attachment structure or structures 32,as well as a gripping feature or features 34 for facilitating handlingof the surgical orientation device 14. The attachment structures 32 canfacilitate attachment of the surgical orientation device 14 to anotherdevice, such as for example the first coupling device 18. In a preferredarrangement, the attachment structures 32 comprise grooves, or channels36, along a portion of the back side of the surgical orientation device14.

The attachment structures 32 can be formed, for example, from protrudingportions of the back side of the surgical orientation device 14, and canextend partially, or entirely, along the back side of the surgicalorientation device 14. The attachment structures 32 can receivecorresponding, or mating, structures from the first coupling device 18,so as to couple, or lock, the first coupling device 18 to the surgicalorientation device 14.

FIGS. 5-7 show a top side 38 and bottom side 40 of the surgicalorientation device 14. In some embodiments the surgical orientationdevice 14 can include optical components 42 located on the top side 38,the bottom side 40, or both the top and bottom sides 38, 40 of thesurgical orientation device 14. The optical components 42 can comprisetransparent windows 44 integrated into the surgical orientation device14. The optical components 42 can be windows that permit visible light(e.g. laser light) to emit from the top side 38, the bottom side 40, orboth the top and bottom sides 38, 40 of the surgical orientation device14. While the embodiment illustrated in FIGS. 6 and 7 shows two windows44 for transmitting light, other numbers are also possible, includinghaving no windows 44 or optical components 42. Additionally, while theoptical components 42 are shown located on the top and bottom of thesurgical orientation device 14, in other embodiments the opticalcomponents 42 can be located in other positions and/or on other portionsof the surgical orientation device 14.

FIG. 8 illustrates a high-level block diagram of an embodiment of anelectrical system 1100 of the surgical orientation device 14. Theelectrical system 1100 can comprise an electronic control unit 1102 thatcommunicates with one or more sensor(s) 1104, one or more optionalvisible alignment indicators 1106, a power supply 1108, a display 1110,external memory 1112, one or more user input devices 1114, other outputdevices 1116, and/or one or more input/output (“I/O”) ports 1118.

In general, the electronic control unit 1102 can receive input from thesensor(s) 1104, the external memory 1112, the user input devices 1114and/or the I/O ports 1118, and can control and/or transmit output to theoptional visible alignment indicators 1106, the display 1110, theexternal memory 1112, the other output devices 1116 and/or the I/O ports1118. The electronic control unit 1102 can be configured to receive andsend electronic data, as well as perform calculations based on receivedelectronic data. In certain embodiments, the electronic control unit1102 can be configured to convert the electronic data from amachine-readable format to a human readable format for presentation onthe display 1110. The electronic control unit 1102 can comprise, by wayof example, one or more processors, program logic, or other substrateconfigurations representing data and instructions, which can operate asdescribed herein. In some embodiments, the electronic control unit 1102can comprise a controller circuitry, processor circuitry, processors,general purpose single-chip or multi-chip microprocessors, digitalsignal processors, embedded microprocessors, microcontrollers and/or thelike. The electronic control unit 1102 can have conventional addresslines, conventional data lines, and one or more conventional controllines. In some embodiments, the electronic control unit 1102 cancomprise an application-specific integrated circuit (ASIC) or one ormore modules configured to execute on one or more processors. In someembodiments, the electronic control unit 1102 can comprise an AT91 SAM7SE microcontroller available from Atm el Corporation.

The electronic control unit 1102 can communicate with internal memoryand/or the external memory 1112 to retrieve and/or store data and/orprogram instructions for software and/or hardware. The internal memoryand the external memory 1112 can include random access memory (“RAM”),such as static RAM, for temporary storage of information and/or readonly memory (“ROM”), such as flash memory, for more permanent storage ofinformation. In some embodiments, the external memory 1112 can includean AT49BV160D-70TU Flash device available from Atmel Corporation and aCY62136EV30LL-45ZSXI SRAM device available from Cypress SemiconductorCorporation. The electronic control unit 1102 can communicate with theexternal memory 1112 via an external memory bus.

In general, the sensor(s) 1104 can be configured to provide continuousreal-time data to the surgical orientation device 14. The electroniccontrol unit 1102 can be configured to receive the real-time data fromthe sensor(s) 1104 and to use the sensor data to determine, estimate,and/or calculate an orientation or position of the surgical orientationdevice 14. The orientation information can be used to provide feedbackto a user during the performance of a surgical procedure, such as atotal knee joint replacement surgery, as described in more detailherein.

In some arrangements, the one or more sensors 1104 can comprise at leastone orientation sensor configured to provide real-time data to theelectronic control unit 1102 related to the motion, orientation, and/orposition of the surgical orientation device 14. For example, the one oremore sensors 1104 can comprise at least one gyroscopic sensor,accelerometer sensor, tilt sensor, magnetometer and/or other similardevice or devices configured to measure, and/or facilitate determinationof, an orientation of the surgical orientation device 14. In someembodiments, the sensors 1104 can be configured to provide measurementsrelative to a reference point(s), line(s), plane(s), and/orgravitational zero. Gravitational zero, as referred to herein, refersgenerally to an orientation in which an axis of the sensor isperpendicular to the force of gravity, and thereby experiences noangular offset, for example tilt, pitch, roll, or yaw, relative to agravitational force vector. In some embodiments, the sensor(s) 1104 canbe configured to provide measurements for use in dead reckoning orinertial navigation systems.

In some embodiments, the sensor(s) 1104 can comprise one or moreaccelerometers that measure the static acceleration of the surgicalorientation device 14 due to gravity. For example, the accelerometerscan be used as tilt sensors to detect rotation of the surgicalorientation device 14 about one or more of its axes. The one or moreaccelerometers can comprise a dual axis accelerometer (which can measurerotation about two axes of rotation) or a three-axis accelerometer(which can measure rotation about three axes of rotation). The changesin orientation about the axes of the accelerometers can be determinedrelative to gravitational zero and/or to a reference plane registeredduring a tibial or femoral preparation procedure as described herein. Inone embodiment, the sensor(s) 1104 can comprise a three-axis gyroscopicsensor and a three-axis accelerometer sensor.

In some embodiments, a multi-axis accelerometer (such as the ADXL203CEMEMS accelerometer available from Analog Devices, Inc. or the LIS331DLHaccelerometer available from ST Microelectronics.) can detect changes inorientation about two axes of rotation. For example, the multi-axisaccelerometer can detect changes in angular position from a horizontalplane (e.g., anterior/posterior rotation) of the surgical orientationdevice 14 and changes in angular position from a vertical plane (e.g.,roll rotation) of the surgical orientation device 14. The changes inangular position from the horizontal and vertical planes of the surgicalorientation device 14 (as measured by the sensor 1104) can also be usedto determine changes in a medial-lateral orientation (e.g., varus/valgusrotation) of the surgical orientation device 14.

In some arrangements, the sensor(s) 1104 comprise at least one single-or multi-axis gyroscope sensor and at least one single- or multi-axisaccelerometer sensor. For example, the sensor(s) 1104 can comprise athree-axis gyroscope sensor (or three gyroscope sensors) and athree-axis accelerometer (or three accelerometer sensors) to providepositional and orientational measurements for all six degrees of freedomof the surgical orientation device 14. In some embodiments, thesensor(s) 1104 can provide an inertial navigation or dead reckoningsystem to continuously calculate the position, orientation, and velocityof the surgical orientation device 14 without the need for externalreferences.

In some embodiments, the sensors 1104 can comprise one or moreaccelerometers and at least one magnetometer. The magnetometer can beconfigured to measure a strength and/or direction of one or moremagnetic fields in the vicinity of the surgical orientation device 14and/or the reference sensor. The magnetometer can advantageously beconfigured to detect changes in angular position about a horizontalplane. In some embodiments, the sensor(s) 1104 can comprise one or moresensors capable of determining distance measurements. For example asensor located in the surgical orientation device 14 can be inelectrical communication (wired or wireless) with an emitter elementmounted at the end of a measurement probe. In some embodiments, theelectronic control unit 1102 can be configured to determine the distancebetween the sensor and emitter (for example, an axial length of ameasurement probe corresponding to a distance to an anatomical landmark,such as a malleolus).

In some embodiments, the one or more sensors 1104 can comprise atemperature sensor to monitor system temperature of the electricalsystem 1100. Operation of some of the electrical components can beaffected by changes in temperature. The temperature sensor can beconfigured to transmit signals to the electronic control unit 1102 totake appropriate action. In addition, monitoring the system temperaturecan be used to prevent overheating. In some embodiments, the temperaturesensor can comprise a NCP21WV103J03RA thermistor available from MurataManufacturing Co. The electrical system 1100 can further includetemperature, ultrasonic and/or pressure sensors for measuring propertiesof biological tissue and other materials used in the practice ofmedicine or surgery, including determining the hardness, rigidity,and/or density of materials, and/or determining the flow and/orviscosity of substances in the materials, and/or determining thetemperature of tissues or substances within materials.

In some embodiments, the sensor(s) 1104 can facilitate determination ofan orientation of the surgical orientation device 14 relative to areference orientation established during a preparation and alignmentprocedure performed during orthopedic surgery.

The one or more sensor(s) 1104 can form a component of a sensor modulethat comprises at least one sensor, signal conditioning circuitry, andan analog-to-digital converter (“ADC”). In some embodiments, thecomponents of the sensor module can be mounted on a stand-alone circuitboard that is physically separate from, but in electrical communicationwith, the circuit board(s) containing the other electrical componentsdescribed herein. In some embodiments, the sensor module can bephysically integrated on the circuit board(s) with the other electricalcomponents. The signal conditioning circuitry of the sensor module cancomprise one or more circuit components configured to condition, ormanipulate, the output signals from the sensor(s) 1104. In someembodiments, the signal conditioning circuitry can comprise filteringcircuitry and gain circuitry. The filtering circuitry can comprise onemore filters, such as a low pass filter. For example, a 10 Hz singlepole low pass filter can be used to remove vibrational noise or otherlow frequency components of the sensor output signals. The gaincircuitry can comprise one or more operational amplifier circuits thatcan be used to amplify the sensor output signals to increase theresolution potential of the sensor(s) 1104. For example, the operationalamplifier circuit can provide gain such that a 0 g output results in amidrange (e.g., 1.65 V signal), a+1 g output results in a full scale(e.g., 3.3 V) signal and a-1 g output results in a minimum (0 V) signalto the ADC input.

In general, the ADC of the sensor module can be configured to convertthe analog output voltage signals of the sensor(s) 1104 to digital datasamples. In some embodiments, the digital data samples comprise voltagecounts. The ADC can be mounted in close proximity to the sensor toenhance signal to noise performance. In some embodiments, the ADC cancomprise an AD7921 two channel, 12-bit, 250 Kiloseconds per Sample ADC.In an arrangement having a 12-bit ADC, the 12-bit ADC can generate 4096voltage counts. The ADC can be configured to interface with theelectronic control unit 1102 via a serial peripheral interface port ofthe electronic control unit 1102. In some embodiments, the electroniccontrol unit 1102 can comprise an on-board ADC that can be used toconvert the sensor output signals into digital data counts.

With continued reference to FIG. 8, in some embodiments the optionalvisible alignment indicators 1106 can comprise one or more lasers, whichcan be configured to project laser light through the optical componentor components 42 described above. For example, the optional visiblealignment indicators 1106 can comprise a forward laser and an aft laser.The laser light can be used to project a point, a plane, and/or across-hair onto a target or targets, including but not limited to ananatomical feature or landmark, to provide alternative or additionalorientation information to a surgeon regarding the orientation of theorientation device 14. For example, laser light can be used to project aplane on a portion of bone to indicate a resection line and a cross-hairlaser pattern can be used to ensure alignment along two perpendicularaxes. In certain embodiments, the visible alignment indicators 1106 canbe used to determine a distance to an anatomical feature or landmark(for example, a laser distance measurement system). For example, theelectronic control unit 1102 can project laser light to a target and asensor 1104 within the surgical orientation device can sense the laserlight reflected back from the target and communicate the information tothe electronic control unit 1102. The electronic control unit 1102 canthen be configured to determine the distance to the target. The laserscan be controlled by the electronic control unit 1102 via pulse widthmodulation (“PWM”) outputs. In some embodiments, the visible alignmentindicators 1106 can comprise Class 2M lasers. In other embodiments, thevisible alignment indicators 1106 can comprise other types of lasers orlight sources.

The power supply 1108 can comprise one or more power sources configuredto supply DC power to the electronic system 1100 of the surgicalorientation device 14. In certain embodiments, the power supply 1108 cancomprise one or more rechargeable or replaceable batteries and/or one ormore capacitive storage devices (for example, one or more capacitors orultracapacitors). In some embodiments, power can be supplied by otherwired and/or wireless power sources. In preferred arrangements, thepower supply 1108 can comprise two AA alkaline, lithium, or rechargeableNiMH batteries. The surgical orientation device 14 can also include aDC/DC converter to boost the DC power from the power supply to a fixed,constant DC voltage output (e.g., 3.3 volts) to the electronic controlunit 1102. In some embodiments, the DC/DC converter comprises aTPS61201DRC synchronous boost converter available from TexasInstruments. The electronic control unit 1106 can be configured tomonitor the battery level if a battery is used for the power supply1108. Monitoring the battery level can advantageously provide advancenotice of power loss. In some embodiments, the surgical orientationdevice 14 can comprise a timer configured to cause the surgicalorientation device 14 to temporarily power off after a predeterminedperiod of inactivity and/or to permanently power off after apredetermined time-out period.

As discussed above, the display 1110 (e.g. display 26 seen in FIG. 4)can comprise an LCD or other type screen display. The electronic controlunit 1102 can communicate with the display via the external memory bus.In some embodiments, the electronic system 1100 can comprise a displaycontroller and/or an LED driver and one or more LEDs to providebacklighting for the display 1110. For example, the display controllercan comprise an LCD controller integrated circuit (“IC”) and the LEDdriver can comprise a FAN5613 LED driver available from FairchildSemiconductor International, Inc. The electronic control unit 1102 canbe configured to control the LED driver via a pulse width modulationport to control the brightness of the LED display. For example, the LEDdriver can drive four LEDs spaced around the display screen to provideadequate backlighting to enhance visibility. The display can beconfigured to display one or more on-screen graphics. The on-screengraphics can comprise graphical user interface (“GUI”) images or icons.The GUI images can include instructive images, such as illustratedsurgical procedure steps, or visual indicators of the orientationinformation received from the sensor(s) 1104. For example, the display1110 can be configured to display degrees and either a positive ornegative sign to indicate direction of rotation from a reference planeand/or a bubble level indicator to aid a user in maintaining aparticular orientation. The display 1110 can also be configured todisplay alphanumeric text, symbols, and/or arrows. For example, thedisplay 1110 can indicate whether a laser is on or off and/or include anarrow to a user input button with instructions related to the result ofpressing a particular button.

With continued reference to FIG. 8, the user input device(s) 1114 (e.g.user input devices 28 seen in FIG. 4) can comprise buttons, switches, atouch screen display, a keyboard, a joystick, a scroll wheel, atrackball, a remote control, a microphone, and the like. The user inputdevices 1114 can allow the user to enter data, make selections, inputinstructions or commands to the surgical orientation device 14, verify aposition of the surgical orientation device 14, turn the visiblealignment indicators 1106 on and off, and/or turn the entire surgicalorientation device 14 on and off. The other user output devices 1116(i.e. other than the display 1110) can comprise an audio output, such asa speaker, a buzzer, an alarm, or the like. For example, the audiooutput can provide a warning to the user when a particular conditionoccurs. The output devices 1116 can also comprise a visible output, suchas one or more LED status or notification lights (for example, toindicate low battery level, an error condition, etc.). The audio outputcan comprise different patterns, tones, cadences, durations, and/orfrequencies to signify different conditions or events. In someembodiments, output from the electronic control unit 1102 can be sent toexternal display devices, data storage devices, servers, and/or othercomputing devices (e.g., via a wireless network communication link).

The I/O ports 1118 of the electronic control unit 1102 can comprise aJTAG port and one or more serial communication ports. The JTAG port canbe used to debug software installed on the electronic control unit 1102during testing and manufacturing phases. The JTAG port can be configuredsuch that it is not externally accessible post-manufacture. The serialcommunication ports can include a Universal Serial Bus (“USB”) portand/or one or more universal asynchronous receiver/transmitters (“UART”)ports. At least one of the UART ports can be accessible externallypost-manufacture. The external UART port can be an infrared (“IR”)serial port in communication with an infrared (“IR”) transceiver. The IRserial port can be used to update the software installed on theelectronic control unit 1102 post-manufacture and/or to test theoperation of the electronic control unit 1102 by outputting data fromthe electronic control unit 1102 to an external computing device via anexternal wireless connection. Other types of I/O ports are alsopossible.

FIG. 8A illustrates another high-level block diagram of an embodiment ofan electrical system 1100A that can form a part of a surgicalorientation system. In one embodiment, the surgical orientation systemincludes the surgical orientation device 14 and a reference device 16.In one embodiment, the components schematically grouped in the box “16”can be disposed in a first enclosure of the reference sensor 16 whilethe other components in FIG. 8A can be housed in a second enclosure ofthe orientation device 14. The electrical system 1100A in FIG. 8A can besimilar to the electrical system of FIG. 8. The electrical system 1100Aof FIG. 8A can comprise an electronic control unit 1102A that is adaptedto communicate with one or more sensor(s) 1104, a power supply 1108, adisplay 1110, external memory 1112, one or more user input devices 1114,other output devices 1116, and/or one or more input/output (“I/O”) ports1118. As illustrated in FIG. 8A, the input ports 1118 can be configuredto receive information from an outside source. For example, the inputports 1118 can be configured to receive radio frequency data (RF) fromreference device 16. As illustrated in FIG. 8A, the reference device 16includes in one embodiment a plurality of sensors that together form aninertial measurement unit 1105 (IMU). In particular, the IMU 1105includes a first sensor 1107 for determining acceleration and a secondsensor 1109 for determining gyroscopic positioning. As discussed herein,the first sensor can be an accelerometer and the second sensor can be agyroscopic sensor. The reference device 16 also includes a transmitter1111 for sending data from the sensors to the electrical system 1100A ofthe surgical orientation device 14. The information received from thereference device 16 can be fed to an input port 1118, or alternatively,the electronic control unit 1102 can itself receive the information(e.g., wirelessly as illustrated by the dashed line). The informationfrom the reference device 16 can correspond, for example, to theposition and/or orientation of the reference device 16, and can be usedby the surgical orientation device 14 to determine an aggregate, oroverall, position and/or orientation of the surgical orientation device14.

In alternate embodiments, components of the reference device 16illustrated in FIG. 8A can be incorporated into the surgical orientationdevice 14. For example, the IMU 1105 can be disposed in the surgicalorientation device 14 so that the surgical orientation device can beused to determine the spatial location of an anatomical axis and thereference device can be used for other purposes, such as to trackrelative position changes of a patient's femur, leg, or other bone orlimb.

Referring to FIGS. 8-10, the sensor(s) 1104 can comprise one or moreaccelerometers. Accelerometers can measure the static acceleration ofgravity in one or more axes to measure changes in tilt orientation. Forexample, a three-axis accelerometer can measure the static accelerationdue to gravity along three orthogonal axes, as illustrated in FIG. 10. Atwo-axis accelerometer can measure the static acceleration due togravity along two orthogonal axes (for example, the x and y axes of FIG.9). The output signals of an accelerometer can comprise analog voltagesignals. The output voltage signals for each axis can fluctuate based onthe fluctuation in static acceleration as the accelerometer changes itsorientation with respect to the gravitational force vector. In certainembodiments, an accelerometer experiences static acceleration in therange from −1 g to +1 g through 180 degrees of tilt (with −1 gcorresponding to a −90 degree tilt, 0 g corresponding to a zero degreetilt, and +1 g corresponding to a +90 degree tilt. The accelerationalong each axis can be independent of the acceleration along the otheraxis or axes.

FIG. 10 illustrates a measured acceleration along each of the three axesof a three-axis accelerometer in six different orientation positions.TOP and BOTTOM labels, as well as a circle indicating Pin 1 of theaccelerometer, have been included to aid in determining the variousorientations. A gravitational force reference vector is illustrated aspointing straight down toward the Earth's surface. At positions A and B,the x-axis and the y-axis of the accelerometer are perpendicular to theforce of gravity and the z-axis of the accelerometer is parallel to theforce of gravity; therefore, the x and y acceleration components ofstatic acceleration due to gravity at positions A and B are 0 g and thez component of static acceleration due to gravity at positions A and Bis +1 g and −1 g, respectively. At positions C and E, the x-axis and thez-axis of the accelerometer are perpendicular to the force of gravityand the y-axis is parallel to the force of gravity; therefore, the x andz acceleration components of static acceleration due to gravity atpositions C and E are 0 g and the y component of static acceleration dueto gravity at positions C and E is +1 g and −1 g, respectively. Atpositions D and F, the y-axis and z-axis are perpendicular to the forceof gravity and the x-axis is parallel to the force of gravity;therefore, the y and z acceleration components of static accelerationdue to gravity at positions D and F are 0 g and the x component ofstatic acceleration due to gravity at positions D and F is +1 g and −1g, respectively. A dual-axis accelerometer operates in the same mannerbut without the z component. In certain arrangements, a three-axisaccelerometer can be used as a tiltmeter to measure changes inorientation about two axes.

Multi-axis accelerometers can be conceptualized as having a separateaccelerometer sensor for each of its axes of measurement, with eachsensor responding to changes in static acceleration in one plane. Incertain embodiments, each accelerometer sensor is most responsive tochanges in tilt (i.e., operates with maximum or optimum accuracy and/orresolution) when its sensitive axis is substantially perpendicular tothe force of gravity (i.e., when the longitudinal plane of theaccelerometer sensor is parallel to the force of gravity) and leastresponsive when the sensitive axis is parallel to the force of gravity(i.e., when the longitudinal plane of the accelerometer sensor isperpendicular to the force of gravity). FIG. 11 illustrates the outputof the accelerometer in g's as it tilts from −90 degrees to +90 degrees.As shown, the tilt sensitivity diminishes between −90 degrees and −45degrees and between +45 degrees and +90 degrees (as shown by thedecrease in slope). This resolution problem at the outer ranges of tiltmotion can make the measurements less accurate for tilt measurementsover 45 degrees. In certain embodiments, when the mounting angle of thesurgical orientation device 14 is known, the sensor(s) 1104 can bemounted to be offset at an angle such that the accelerometer sensors canoperate in their more accurate, steeper slope regions. In otherarrangements, the sensor(s) 1104 can be mounted to be offset to accountfor a predetermined range of motion about other axes of rotation aswell. In yet other arrangements, for example, when a multi-axisaccelerometer is used, the accelerometer sensor(s) 1104 can be mountedin parallel with the anterior-posterior axis of the surgical orientationdevice 14. In one multi-axis accelerometer arrangement, a handoff systemcan be incorporated to ensure that the accelerometer sensor(s) 1104 withthe most accurate reading (e.g., <45 degrees) are being used at eachorientation position. The handoff system can employ hysteresis to avoid“bouncing” phenomena during the handoffs between the accelerometersensor(s) 1104. In yet other embodiments, the multi-axis accelerometerscan be mounted without any offset angle.

FIG. 12 illustrates an embodiment of the inside of the surgicalorientation device 14. The surgical orientation device 14 can compriseone or more circuit boards and/or other circuitry capable ofinstallation within the surgical orientation device 14. As illustrated,the surgical orientation device 14 can comprise a sensor board 46 and amain board 48. In some embodiments, the components of the sensor moduledescribed above can be mounted on the sensor board 46 and the othercomponents of the electrical system 1100 can be mounted on the mainboard 48. The sensor board 46 can comprise one or more sensors 50 (e.g.,sensor(s) 1104 as described above). In alternative embodiments, thesensor board 46 and the main board 48 can be combined into a singlecircuit board. The sensor board 46 and the main board 48 can compriserigid or flexible circuit boards. The sensor board 46 and the main board48 can be fixedly or releasably attached to the outer housing 22.

As illustrated, the sensor board 46 can be mounted at an approximately22-degree angle relative to a plane extending longitudinally through thehousing 22, which can be parallel to or co-planar with ananterior-posterior axis of the main board 48. In some embodiments, thesensor board 46 can be mounted at an approximately 0 degree anglerelative to a plane extending longitudinally through the housing 22,which can be parallel to or correspond to an anterior-posterior axis ofthe main board 46. As shown in FIG. 12, the surgical orientation device14 can include two AA, alkaline, lithium, or rechargeable NiMH batteries52 as the power supply 1110 for providing power to the surgicalorientation device 14. In some embodiments, the surgical orientationdevice 14 also can include lasers 54 and 56 as the optional visiblealignment indicators 1106 described above.

In a preferred arrangement, the surgical orientation device 14 describedabove can advantageously be disposed of after use. Once the surgicalorientation device 14 has been used during a total knee replacementprocedure or other medical procedure, the surgical orientation device 14can be discarded, so as to inhibit and/or prevent contamination duringsubsequent procedures and reduce the need for sterilization.

In other embodiments, the surgical orientation device 14 canalternatively have a disposable outer housing 22, such that the internalcomponents of the surgical orientation device (e.g. sensors 50,batteries 52, etc.) can be reused, while the outer housing 22 isdiscarded. For example, with reference to FIG. 13 in some embodimentsthe outer housing can comprise a flap 57 that releases to allow removalof the internal components of the surgical orientation device 14.

Further description of embodiments of a surgical orientation device 14and its sensor(s) can be found in U.S. Patent Application No. U.S.Patent Publication No. 2010/0063508, the contents of which areincorporated herein by reference in their entirety.

B. Device for Coupling the Surgical Orientation Device to AnotherOrthopedic Fixture

Referring to FIG. 14, the first coupling device 18 can be used to attachthe surgical orientation device 14 to another orthopedic fixture.“Orthopedic fixture” is a broad term and is to be given its ordinary andcustomary meaning to a person of ordinary skill in the art (i.e. it isnot to be limited to a special or customized meaning) and includes,without limitation, jigs or other mechanical and/or electricalstructures that can be used in an orthopedic procedure. For example, thefirst coupling device 18 can be used to attach the surgical orientationdevice 14 to the femoral jig assembly 12. The first coupling device 18can advantageously enable the surgical orientation device 14 to bequickly coupled and decoupled with the femoral jig assembly 12 during asurgical procedure. This enables the surgical orientation device 14 tobe used in a modular fashion, with a variety of orthopedic fixtures atone or more stages of a procedure.

The first coupling device 18 can include an orientation device interface58 attached to an interface support member 60. The orientation deviceinterface 58 can be designed to connect with the attachment structures32 of the surgical orientation device 14 described above, therebyfacilitating a secure but releasable attachment between the surgicalorientation device 14 and the femoral jig assembly 12. In oneembodiment, the orientation device interface 58 can be inserted into thegrooves or channels 36 along the back portion of the surgicalorientation device 14 described above.

With continued reference to FIG. 14, the interface support member 60 caninclude jig attachment features 62. The jig attachment features 62 canbe used to mate the first coupling device 18 to a microblock assembly ofthe femoral jig assembly 12 (see, e.g. the microblock assembly 90illustrated in FIGS. 17 and 19). (The term “microblock” is a generalterm, and is not intended to be limited only to assemblies that aresmall in nature. Thus, the term “microblock” can refer to an assembly ofany size.) Mating the jig attachment features 62 with correspondingattachment features of a microblock assembly allows the interfacesupport member 60 to be attached to the microblock assembly in a securebut releasable fashion. The jig attachment features 62 and theattachment features of the microblock assembly can be any suitableattachment structures that provide a secure but releasable attachment,including but not limited to (i) friction or pressure fit features; and(ii) openings, apertures, bores and holes (non-threaded, threaded,partially extended through a structure or entirely through a structure)and corresponding pins or screws (collectively referred hereinafter as“attachment structures”).

While the first coupling device 18 described above can be used to attachand/or couple the surgical orientation device 14 with the femoral jigassembly 12, other methods and devices for attaching and/or coupling thecomponents of the femoral preparation system 10 are also possible.

Additionally, in a preferred arrangement, the femoral jig assembly 12and the first coupling device 18 of the femoral system 10 can bebiocompatible for short term exposure to the inner anatomy of the kneeor other body joint, and can be sterilized by autoclave and/or gas(“autoclavable components”). Other components of the femoral system 10including but not limited to the reference device 16 described below mayoptionally have autoclavable components as well. The autoclavablecomponents can operate without lubricants. Materials for theautoclavable components can be selected and treated to prevent gallingand provide smooth operation consistent with expectations for a highquality surgical instrument. In general, the autoclavable components canbe made robust to withstand normal and abusive use, especially roughhandling during cleaning and/or sterilization.

The components of the femoral system 10 can optionally be etched withpart numbers, revisions levels, and company name and logo. Othermarkings can also be added to provide clarity.

C. Reference Sensor Device

Referring to FIG. 15 , the reference sensor device 16 can be used tomeasure and record the location of anatomical landmarks used in a totalknee procedure, such as the location of the mechanical axis of a leg(and femur). “Reference sensor device” is a broad term and is to begiven its ordinary and customary meaning to a person of ordinary skillin the art (i.e. it is not to be limited to a special or customizedmeaning) and includes, without limitation, any device that can be usedto reference another device, and/or to provide orientation informationor perform calculations identically or similar to the surgicalorientation device 14 described above. In some embodiments, thereference sensor device 16 can comprise the same or similar componentsas the surgical orientation device 14 described above. Furtherdescription of a reference sensor can be found, for example and withoutlimitation, in paragraphs [0176]-[0178] of U.S. patent application Ser.No. 12/509,388, which is incorporated by reference herein.

In a preferred arrangement, the reference sensor device 16 can beconfigured for portable hand-held use. With reference to FIG. 15, in oneembodiment the internal components of the reference sensor device 16 cancomprise a sensor 64 inside of a reference sensor housing 66 (notshown). The reference sensor 64 can include a microcontroller and/orcommunication device such as infrared, RF, Bluetooth or other wirelesstechnology which can relay information from the reference sensor 64 tothe electronic control unit 1102 of the surgical orientation device 14.The reference sensor 64 can be, for example, any one of the sensorsdescribed for use as sensor 1104 (e.g. sensor 50) described above. Thereference sensor device 16 can include a circuit board 70 upon which thecomponents of the reference sensor 64 are mounted thereon. During a kneereplacement procedure, the reference sensor 64 can detect changes inmovement of a femur in a varus/valgus, flexion/extension, and/or otherdirections.

The electronic control unit 1102 of the surgical orientation device 14can be configured to receive information from the reference sensor 64(e.g., a receiver of infrared, RF, Bluetooth™, or other wirelesstechnology) and to combine that information with information from thesensor(s) 50 located within the surgical orientation device 14 tocalculate an overall, or aggregate, movement and orientation of thereference sensor 64 relative to an axial line or plane, for example asillustrated in FIG. 8A. The electronic control unit 1102 in the surgicalorientation device 14 can correct for changes in position of this axisor plane, and the display 26 can indicate to the user an appropriatevarus/valgus and/or flexion/extension angle for resection, based on theactual location of the mechanical axis or plane.

Referring to FIG. 15, the reference sensor device 16 can include acircuit board enclosure 72 and a cover 74. The enclosure 72 can be anopen box of rectangular shape. The reference sensor device 16 canfurther include a battery enclosure 76 and a battery cover 78. Thebattery enclosure 76 can include electric features 80 for electriccommunication between a replaceable battery 82 and the reference sensor64. The electric features 80 can be attached to the battery enclosure 76using various methods (e.g., the screws 84 shown in FIG. 15). Thebattery enclosure 76 and the battery cover 78 can be attached in asecure but releasable fashion using any suitable attachment structures86. For example and referring to FIG. 15, the battery enclosure 76 andthe battery cover 78 can be attached in a secure but releasable fashionusing one or more of the following attachment structures 86: a pin,through holes, and a locking clip. The circuit board enclosure 72, thecover 74 and the circuit board 70 can all be attached together in asecure but releasable fashion using attachment structures 86 such as thescrews and washers shown in FIG. 15.

D. Device For Coupling the Reference Sensor Device to another OrthopedicFixture

Referring to FIG. 16, the reference sensor device 16 can be used in avariety of orthopedic procedures (e.g., femoral and tibial preparationmethods). Accordingly, the housing 66 can optionally include variousstructural features for attachment with a variety of orthopedicfixtures.

For example, the femoral jig assembly 12 can comprise a second couplingdevice 20. The second coupling device 20 can be attached to thereference sensor housing 66. In one embodiment, the second couplingdevice 20 can be securely but releasably attached to the sensor housing66 by common attachment structures. In another embodiment the secondcoupling device 20 can be formed as a structural part of the sensorhousing 66. The second coupling device 20 can include the same orsimilar type of jig attachment features 62 that are on the firstcoupling device 18. The jig attachment features 62 can mate withcorresponding attachment features of a microblock assembly to form asecure but releasable attachment with the femoral jig assembly 12 (see,e.g. the microblock assembly 90 illustrated in FIGS. 17 and 19).

While the second coupling device 20 described above can be used toattach and/or couple the reference sensor device 16 with the femoral jigassembly 12, other methods and devices for attaching and/or coupling thecomponents of the femoral preparation system 10 are also possible.

E. Orthopedic Assembly for Femoral Preparation

Referring to FIG. 17, the femoral jig assembly 12 can comprise anorthopedic assembly for femoral preparation during a total kneereplacement procedure. In a preferred arrangement, the femoral jigassembly 12 can comprise a distal guide assembly 88, a microblockassembly 90, a cutting block 92 and an optional anterior probe 94.

Referring to FIG. 18, the distal guide assembly 88 can comprise amodular paddle 96, an articulating arm 98, a midline guide 100, and amidline pin 102. The articulating arm 98 can be configured to attach tothe microblock assembly 90 and either the cutting block 92 or theanterior probe 94 in a secure but releasable fashion using, for example,the types of attachment structures described above. The arm 98 may beconsidered to articulate at least by being moveably coupled with otherstructures, such as the microblock assembly 90. In some embodiments, thearticulating arm 98 includes a simple rod, arm, or elongate rigid memberthat can swing about an axis between a plurality of positions, asdiscussed below. In one embodiment, the articulating arm 98 can includeposition adjustment features 104 such as notches spaced in a scale ofdesired increment distances (e.g. 1 mm or 2 mm). These notches canfacilitate the adjustment of the position of a cutting block 92 when thearticulating arm 98 is attached to the cutting block 92, resulting inadjustment of the femoral resection depth.

Referring to FIG. 18, the modular paddle 96 can include a channel 106that is adapted to accept the midline guide 100. The channel 106 canallow the midline guide 100 to move or slide up and down the channel106. Adjacent the channel 106, the modular paddle 96 can includereference markings 108. The reference markings 108 can be provided in ascale of desired increment distances (e.g., 1 mm or 2 mm increments orthe like). The midline guide 100 can include a midline pin receivingfeature 110 that allows an insert portion 112 of the midline pin 102 topass through the midline guide 100. The midline pin 102 can include boththe insert portion 112 and a knob portion 114. The knob portion 114 canbe designed for interaction with a user allowing the user to move themidline pin 102 up and down the modular paddle 96 (e.g., in aflexion/extension direction upon attachment to a distal end portion of afemur during femoral preparation methods). The insert portion 112 can bedesigned to have a suitable length that allows the midline pin 102 toenter and pass through the midline guide 100 and into a desired depth ofa distal end portion of a femur.

Referring to FIG. 19, the microblock assembly 90 can include amicroblock member 116, a translating member 118, and a translationstructure or structures 120. The microblock member 116 and thetranslating member 118 can both include an attachment feature orfeatures 122 for secure but releasable attachment with each other, thearticulating arm 98, the cutting block 92, the anterior probe 94, thefirst coupling device 18, and/or the second coupling device 20.

Both the microblock member 116 and the translating member 118 caninclude translation receiving features 124. The translation receivingfeatures 124 can allow both the microblock member 116 and thetranslating member 118 to receive the translation structures 120, withfirst ends 126 of the translation structures 120 attached to thetranslating member 118 and second ends 128 of the translation structures120 attached to the microblock member 116. The second ends 128 of thetranslation structures 120 can include a translation adjustment feature130 (e.g. slot or socket for receiving a tool such as a screwdriver)that can be used to move the first ends 126 of the correspondingtranslation structure 120 to cause a desired directional movement oftranslating member 118 (e.g., in a varus/valgus direction or in aflexion/extension direction when the microblock assembly 90 is attachedto the distal end portion of a femur). At least one of the translationreceiving features 124 of the translating member 118 can be adapted toallow movement of the translating member 118 in a varus/valgus directionwhen the microblock assembly 90 is attached to the distal end portion ofa femur. Additionally, at least another one of the translation receivingfeatures 124 of the translating member 118 can be adapted to allowmovement of the translating member 118 in a flexion/extension directionwhen the microblock assembly 90 is attached to the distal end portion ofa femur. The design described above can allow the translationstructure(s) 120 to move at least a portion of the microblock assembly90 (and any other components attached to the microblock assembly 90) ina varus/valgus direction and/or in a flexion/extension direction. Thetranslation structure's ability to move at least a portion of themicroblock assembly 90 can be controlled by the translation adjustmentfeatures 130.

In one embodiment and referring to FIG. 19, the translation structures120 are ball screws, the translation adjustment features 130 arefeatures for receiving a hex driver (not shown) or the like, and thetranslation receiving features 124 are channels contained within thetranslating member 118. At least one of the channels can run in avarus/valgus direction and at least another can run in aflexion/extension direction. To move the translating member 118 of themicroblock assembly 90 (and any other components attached to thetranslating member 118) in a varus/valgus direction and/or in aflexion/extension direction using the translation structures 120, thetranslation adjustment features 130 can each be turned by a hex driverin either a clockwise or a counter-clockwise direction.

Referring to FIG. 19, the microblock member 116 can also includemultiple microblock pin receiving features 132 such as through holes orthe like which allow microblock pins (not shown) to attach themicroblock assembly 90 (and other components of the femoral preparationsystem 10) to the distal end portion of a femur. In some embodiments,the microblock pin receiving features 132 can be angled inward andposteriorly.

Referring to FIGS. 20 and 21, the cutting block 92 can include at leastone opening 134configured to receive a cutting tool such as for examplea cutting saw and/or other referencing tool. The cutting block 92 canfurther include receiving features 136 for receiving, for example (i)corresponding attachment features 122 from the microblock assembly 90;(ii) the articulating arm 98 from the distal guide assembly 88; and(iii) positional pins (not shown) for a secure but releasable attachmentto the microblock assembly 90, the distal guide assembly 88, and/or thedistal portion of a femur. In one embodiment, the receiving features 136for receiving the articulating arm 98 of the distal guide assembly 88can include one or more through holes and/or other features along whichthe cutting block 92 can be moved. The movement of the cutting block 92can be controlled and adjusted based upon the position adjustmentfeatures 104 of the articulating arm 98 as shown in FIG. 18. Forexample, the cutting block 92 can comprise a window or opening 137through which the position adjustment features 104 of the articulatingarm 98 can be seen as the cutting block 92 is moved along thearticulating arm 98.

Referring to FIGS. 19, 20, 21, and 28, the cutting block 92 can be usedfor distal femoral resection during a femoral preparation method. Thecutting block 92 can be oriented and translated in a varus/valgusdirection and a flexion/extension direction by other components of thefemoral preparation system 10 during the femoral preparation method,providing at least two degrees of freedom. During the femoralpreparation method, the cutting block's attachment to the articulatingarm 98 can provide an initial placement of the cutting block 92 adjacentto the distal end portion of a femur 82. Thereafter, the microblockassembly 90 can be used to physically adjust the orientation of thecutting block 92 when the cutting block 92 is attached to the microblockassembly 90 and the microblock assembly 90 is attached to the distal endportion of the femur.

Referring to FIGS. 19, 20, and 28, the physical adjustment of theorientation of the cutting block 92 can be achieved by adjusting thetranslation adjustment features 130 of the translation structures 120 asdiscussed above. For example and referring to FIG. 19, the translationstructure 120 can comprise two ball screws, and the translationadjustment feature 130 of each of the translation structures 120 cancomprise a feature for receiving a hex driver. Turning the translationadjustment feature 130 of one of the ball screws in a clockwisedirection or counter clockwise direction can change the cutting angle ofthe cutting block 92 in a flexion-extension direction. Turning thetranslation adjustment feature 130 of the other one of the ball screwscan change the cutting angle of the cutting block 92 in a varus-valgusdirection. In some embodiments, the translation structures 120 canfacilitate pivoting of the cutting block 92 within a range ofapproximately twenty degrees (e.g. +-ten degrees on either side of apredetermined angle). Other ranges are also possible.

Referring to FIGS. 23 and 24, the anterior probe 94 can be a memberadapted to be attached in a secure but releasable fashion to, forexample, (i) the articulating arm 98 of the distal guide assembly 88; or(ii) the microblock assembly 90. During a femoral preparation method,the anterior probe 94 can extend from the microblock assembly 90 to ananterior cortex 138 of a femur 140. The anterior probe 94 can beadjustable via push button, screw, or other mechanism to assist inreferencing the anterior cortex 138. The anterior probe 138 can allowthe femoral jig assembly 12 to be stabilized in an approximate desiredflexion angle during a femoral preparation method.

III. Femoral Preparation Methods

Referring to FIGS. 22-31, the femoral preparation system 10 describedabove can be used to prepare the femur for a total knee replacement.

A. Attaching an Orthopedic Assembly on a Femur

Referring to FIG. 22, in preparation for the distal femoral resection,the method can begin with locating a distal point that is intersected bythe mechanical axis of the femur.

In one technique for locating a distal point of the mechanical axis ofthe femur 140, a distal end portion 142 of the femur is exposed usingany conventional surgical technique. The tibia 144 and the femur 140 canthen be placed in approximately 90 degrees of flexion as shown in FIG.22. It is possible to place the leg in other degrees of flexion.

A small hole 146 for receiving a portion of the midline pin 102 can thenbe drilled using any conventional surgical technique at an appropriateanatomical location within the distal end portion 142. The anatomicallocation can be the center of the intercondylar notch, a location nearthe insertion of the anterior cruciate ligament (“ACL”), an entry pointto the intramedullary canal, or other suitable anatomical landmark orcombination of landmarks within the distal end portion 142. In oneembodiment, the small hole 146 can be drilled at the approximate centerof the intercondylar notch as shown in FIG. 22.

The method can further comprise installing the femoral jig assembly 12onto the distal end portion 142 by inserting the midline pin 102 intothe small hole 146 as shown in FIGS. 22 and 23. Placement of the midlinepin 102 in the approximate center of the intercondylar notch places thefemoral jig assembly 12 in an approximate center position of the distalend portion 142 and the modular paddle 96 on distal condyles 148 of thefemur 140. The modular paddle 96 can then be fitted to a distal apex ofthe distal condyles 148 thereby allowing the femoral jig assembly 12 tobe placed in an approximate neutral varus/valgus direction as shown inFIG. 23.

The method can further include an optional step of adjusting theanterior probe 94 by placing the anterior probe 94 on the anteriorcortex 138 of the femur 140. The anterior probe 94 can be adjusted viapush button, screw, or other mechanism to assist in referencing theanterior cortex 138 as shown in FIG. 23. Placement of the anterior probe94 on the anterior cortex 138 can allow the femoral jig assembly 12 tobe stabilized in the approximate desired flexion angle. In someembodiments the femoral jig assembly 12 does not need to be preciselyset in a flexion/extension direction. Rather, the initial placement canserve as a visual tool to avoid hyper-flexion or hyper-extension.

Once the femoral jig assembly 12 is placed by the midline pin 102 in anapproximate neutral varus/valgus orientation or angle and by theanterior probe 94 in the approximate desired flexion angle, the methodcan further include verifying the rotational positioning of the femoraljig assembly 12 in an effort to ensure that the femoral jig assembly 12is in the desired position. In one embodiment, the desired position maybe less than about 15 degrees rotation relative to a Whitesides line orepicondylar axis. In another embodiment, the desired position may rangefrom about 0 degrees to about 30 degrees relative to a Whitesides lineor epicondylar axis. This verification process can be completed byobtaining the information provided by the reference markings 108 of themodular paddle 96. The reference markings 108 can inform the user of anoffset distance 150 (see, e.g., FIG. 2B) of the reference sensor device16 in a frontal plane or a flexion/extension direction (e.g. an “APOffset Data”). The AP Offset Data can generally be the offset distance150 measured from a reference point on the reference device 16, such asthe center of the sensor 64 in the reference device 16, to a referencepoint on the femoral jig assembly 12, such as the center of the midlinepin 102 as shown in FIG. 2B. Upon completion of this verificationprocess, the method can include inserting microblock pins 152 into theappropriate microblock pin receiving features 132, allowing themicroblock assembly 90 to be attached to the distal femoral condyles 148in an approximate desired position as shown in FIG. 24.

Once the microblock assembly 90 is attached to the distal femoralcondyles 148, the method can include noting the indicia of distanceprovided by the reference markings 108 and the location of the midlinepin 102 in relation to the reference markings 108 in order to establishthe AP Offset Data discussed above. The AP Offset Data can then beentered into the surgical orientation device 14. In some embodiments,this process of obtaining and entering AP Offset Data into the surgicalorientation device 14 can be avoided if a fixed offset distance isprovided by the configuration of the femoral preparation system 10.

Referring to FIG. 25, the method can further include removing the distalguide assembly 88 and the anterior probe 94 from the femoral jigassembly 12, leaving only the microblock assembly 90 present andattached to the distal condyles 148.

Referring to FIG. 26, the method can further include attaching thesurgical orientation device 14 and the reference sensor device 16 to themicroblock assembly 90 using the first coupling device 18 and secondcoupling device 20 and their respective components for attachment asdiscussed above. Once the surgical orientation device 14 and thereference sensor device 16 are attached to the microblock assembly 90,the method can further include placing the leg in extension as shown inFIG. 27.

In the method thus far, a distal point corresponding to the mechanicalaxis of the femur can be approximated by using a portion of the femoraljig 12 to locate the center of the femur. In addition to the aboveanatomy that can approximate this location, a clinician can employ amethod that considers the most distal point of the sulcus of thetrochlea to correspond to the distal portion of the mechanical axis. Insome embodiments, the IMU is offset a certain distance from the centerof the distal femur. This offset can be accounted for by using the APOffset Data, as discussed above. This offset can be communicated to thesurgical orientation device 14 so that the system can factor it in itscalculation of the mechanical axis. For example, in certain embodiments,the reference sensor 16 encloses the IMU 1105 and is spaced a variabledistance anterior to the center of the distal femur. This distance canbe entered into the surgical orientation device 14 to eliminate a biaserror that would be created by this offset. In other embodiments,instrumentation can be provided that eliminates the variability of thisdistance, such that the distance between the IMU (e.g., incorporatedinto the reference sensor 16) and the center of the femur is constant.In that case, the surgical orientation device 14 or a system employingthe surgical orientation device 14 can be configured to automaticallyeliminate this bias error.

B. Calculating the Location of the Mechanical Axis Using an OrientationDevice

Referring to FIG. 27, in a preferred embodiment, an orientation devicecan be used to calculate the location of the mechanical axis in thefemur. For example, the reference sensor device 16 and/or orientationdevice 14 can be used to determine the relative coordinates of a centerpivot point on the femur. By determining the coordinates of the pivotpoint of the femoral head 154, the reference sensor device 16 and/orsurgical orientation device 14 can calculate the location and/ororientation of the mechanical axis that extends through the femur.

In order to determine the coordinates of the pivot point of the femoralhead 154 (i.e. the pivot point of the mechanical axis), the leg can bemoved (e.g. swung). For example, the leg can be moved in severaldifferent directions and/or planes (see arrows in FIG. 27), with thereference sensor device 16 and/or surgical orientation device 14attached. Readings such as angular rate and acceleration (“surgicalorientation device 14 and/or reference sensor device 16 data”) of thefemur 140 can be obtained by the reference sensor device 16 and/orsurgical orientation device 14 until the location and/or orientation ofthe mechanical axis of the leg and the femur 140 (“femoral mechanicalaxis”) is found. In one embodiment, where one or more multi-axis (e.g.,two-axis) accelerometers and gyroscopes are used, surgical orientationdevice 14 and/or reference sensor device 16 data for each movement ofthe femur 140 can be numerically integrated over time to obtain atrajectory of position and velocity points (one point for each IMUdata). The IMU data can be integrated without imposing any planetrajectory constraints on movements of the femur 140.

The acceleration and angular rate sensed by the reference sensor device16 and/or surgical orientation device 14 during the leg movement can beprocessed while the leg is moved about its pivot point. The referencesensor device 16 and/or surgical orientation device 14 can provide anoutput vector representing the center of the rotation with respect tothe inertial sensor axes of the reference sensor device 16 and/orsurgical orientation device 14.

The IMU data can be input to a microprocessor in the reference sensordevice 16 and/or surgical orientation device 14. In a preferredembodiment, the microprocessor can be located on the reference sensordevice 16, and output from the microprocessor of the reference sensordevice 16 can be transmitted via an RF wireless link to the surgicalorientation device 14. The leg can be moved about its pivot point whileinertial data is being processed by the microprocessor. An algorithmimplemented on the microprocessor can process the inertial data in realtime and determine if the leg is static or dynamically moving. Data fromboth states can be used by the algorithm to determine the pivot point.

The method of calculating the location and/or orientation of themechanical axis described herein, and for calculating in general thelocation and/or orientation of any axis based on a pivot point, canprovide accurate determination of pivot point location and radius ofcurvature without the burdensome and sometimes near impossiblerestraints of external measurements encountered in medical procedures.For example, the method can permit calculation of pivot points in blindsituations where the end joint is typically hidden or unobservable, suchas for the case of the head of a femur.

Examples of three possible leg movement trajectories for calculating theIMU data are: (i) a horizontal swing from the leg's position of originto the surgeon's right and then back again; (ii) a horizontal swing fromthe origin to the surgeon's left and then back again; and (iii) avertical swing upward and then back again. In some protocols, at leastone horizontal movement and at least one vertical movement are includedto provide IMU data. During each swing trajectory the IMU data can bestored for future processing.

In some embodiments, the mechanical axis can be detected by movingand/or swinging the leg when it is attached to the surgical orientationdevice 14 and the reference sensor device 16 on a horizontal plane (e.g.a plane along the operating table), starting from a known fixed positionand orientation (“home position”, which can be close to the surface ofthe horizontal plane) and obtaining IMU data. The arrows shown in FIG.27 illustrate at least one example of how the direction or directionsthe leg 100 can be moved. In one embodiment, the leg can be placed infull extension and subjected to the following movements: (i) abductingthe leg about 30 degrees and returning the leg substantially to a homeposition; and (ii) raising the leg about 30 degrees and returning theleg substantially to a home position. The abduction can occur before theraising movement or vice versa. During the placement and movementsdiscussed above, the leg can stay extended and the microblock assembly90 (including the microblock pins 152 attaching the microblock assembly90 to the distal condyles 148) can clear the tibia 144 through a fullrange of motion. In some embodiments, the leg can be abducted about 20degrees and returned to the home position, and raised about 20 degreesand returned to the home position. In yet other embodiments, the leg canbe abducted between about 10 degrees and returned to the home position,and raised between about 10 degrees and returned to the home position.In yet other embodiments, the leg can be abducted between about 5degrees and returned to the home position, and raised between about 5degrees and returned to the home position. Other ranges and degrees ofmovement are also possible. In some embodiments, the leg can be swung inone generally looping motion from a home position back to the homeposition, the looping motion causing both an abduction and raising ofthe leg.

The reference sensor device 16 and/or surgical orientation device 14,which can be coupled to the leg during such movements, can have axesangled with respect to an axis of the sensor(s) disposed in thereference device 16 and/or in the surgical orientation device 14. Forexample, as illustrated in FIG. 12, the sensor board 46 can be mountedat an acute angle to a plane extending longitudinally through thehousing 22. In other embodiments, the reference sensor device 16 and/orsurgical orientation device 14 have axes that are not angled, e.g.,parallel to or co-planar with, an axis of the reference sensor deviceand/or surgical orientation device 14.

As the leg is swung, the sensors inside the reference sensor device 16and/or surgical orientation device 14 can detect movement of thereference sensor device 16 and/or surgical orientation device 14,collect IMU data on this movement, and transmit the IMU data to, forexample, the surgical orientation device 14. From receiving all of theIMU data transmitted from the sensors inside both the surgicalorientation device 14 and reference sensor device 16, the referencesensor device 16 and/or surgical orientation device 14 can thencalculate, and in some cases display, the location of the center ofrotation of the femur 140, the center of the femoral head 154, and/orthe femoral mechanical axis.

In a preferred arrangement, where the surgical orientation device 14 isdisposable and the reference sensor device 16 is reusable, the referencesensor 16 can be configured to take measurements as the femur is movedto calculate the center of femoral rotation, while the surgicalorientation device 14 can be configured to receive information from thereference sensor device 16 and/or to display information on display 26.In such an arrangement, the surgical orientation device 14 can comprisea multi-axis accelerometer, and the reference sensor device can compriseboth a multi-axis accelerometer and a multi-axis gyroscope. In thismanner, the more expensive components necessary to make suchcalculations can be incorporated into the re-usable reference sensordevice 16. However, in other embodiments the surgical orientation device14, rather than the reference sensor device 16, can include theadditional components and/or sensors necessary to calculate the centerof femoral rotation.

Various formulae, which can be derived from basic centripetalacceleration physics coupled with optimal estimation or Kalman filteringtechniques, can be used during the process described above to performthe calculations in the reference sensor device 16 or surgicalorientation device 14.

C. Error Correction Technique to Remove Biases

In some embodiments, prior to determining the location and/ororientation of the center of rotation of the mechanical axis, an errorcorrection technique can be used to remove biases in the surgicalorientation device 14 and/or reference sensor device 16. For example, anerror correction technique can include assessing 1) static bias; 2)gyroscopic bias; and 3) accelerometer bias in the surgical referencesensor device 16 and/or surgical orientation device 14.

1. Static Bias Determination

In a preferred embodiment, static bias determination can compriseacquiring data from the IMU of the reference sensor device 16 and/orsurgical orientation device 14 in a static condition. This staticcondition can provide a baseline for the reference sensor device 16and/or surgical orientation device 14 and can permit determination ofbiases for internal sensor(s).

For example, once a user is ready to commence the method of determiningthe center point of rotation of the mechanical axis as described above,the user can press a user input 28 on the surgical orientation device14. Once the user input 28 is pressed, the surgical orientation device14 can indicate that the user should hold the surgical orientationdevice 14 motionless. The user can be required to hold the surgicalorientation device 14 motionless for a given period of time. In apreferred embodiment, the user can be required to hold the surgicalorientation device 14 motionless for approximately three seconds, thoughother times or ranges or times are also possible. For example, in someembodiments the user can be required to hold the surgical orientationdevice motionless for at least one but no more than three seconds. Byholding the surgical orientation device motionless, any static biasescan be determined, and can subsequently be removed (e.g. subtracted)during data acquisition.

In some embodiments, if the user does not hold the surgical orientationdevice 14 still for a long enough period, a fail condition can bedisplayed on the surgical orientation device 14, and the user can berequired to start over again by pressing the user input 28.

Inclusion of a gravitation vector can be used for more accurate finalresults. For example, initial orientation of the reference sensor device16 and/or surgical orientation device 14 during static biasdetermination can be used to create an initial gravity vectortransformation matrix relating the orientation of the IMU to theinertial gravity vector. Angular rate data can be used to propagate theattitude of the reference sensor device 16 and/or surgical orientationdevice 14 and update the inertial gravity vector transformation matrixduring subsequent motion.

2. Gyroscope and Accelerometer Bias Determination

Removing gyroscope and accelerometer biases can help to correct forerrors that may arise from starting and stopping in a rotatedorientation. A gyroscope bias determination can comprise, for example,propagating a direction cosine matrix (DCM) using rate sensors in thesurgical orientation device 14 and/or reference sensor device 16. Anaccelerometer bias determination can comprise, for example, propagatinga direction cosine matrix from the gyro bias to remove a gravitycomponent of the accelerometers.

In order to determine gyroscope and accelerometer bias in the surgicalorientation device 14 and/or reference sensor device 16, the leg (withsurgical orientation device 14 and/or reference sensor device 16attached) can be moved by an operator or other means in such a way thatsufficient rate and acceleration data is achieved for all axes. In apreferred arrangement, during this data acquisition phase, and/or anyother phase for error correction or data collection during an orthopedicmethod, the reference sensor device 16 and/or surgical orientationdevice 14 can determine, without user intervention, what phase of datacollection it is in, static or dynamic. In contrast, in some embodimentsthe user can press a user input 28, for example, to tell the referencesensor device 16 and/or surgical orientation device 14 that it is in astatic or dynamic state.

During gyroscope and accelerometer bias determination, the leg can bemoved (e.g. swung through at least different two planes), and an averageangular rate of leg movement of at least 30 degrees per second can beprovided to acquire data, though other rates are also possible. Forexample, in some embodiments an average angular rate of at least 20degrees can suffice. In yet other embodiments an average angular rate ofat least 10 degrees can suffice.

In a preferred arrangement, the leg can be moved in more than one plane,or for example in a loop configuration, and a beginning and endingattitude of the leg after leg movement is complete can be within 15degrees on any axis, though other beginning and ending attitudes arealso possible. In a preferred arrangement, the leg can be swung andreturned back to its home position within approximately 2 cm in theabduction plane, though other ranges and values are also possible.

In a preferred embodiment, the surgical orientation device 14 and/orreference sensor device 16 can advantageously detect when motion (e.g.swinging) of the leg has stopped, and can detect if the leg has returnedto its home (i.e. starting) position. For example, the surgicalorientation device 14 and/or reference sensor device 16 can include a 1Hz filter to prevent false stopping detection. The surgical orientationdevice 14 and/or reference sensor device 16 can average the rate ofmotion over half a second to determine whether the movement of the leg,and consequently the movement of the surgical orientation device 14and/or reference sensor device 16, has come to a stop.

By moving (e.g. swinging) the leg in the manner described above andreturning it to a home position, gyroscope and accelerometer biases canbe accounted for in the surgical orientation device 14 and/or referencesensor device 16. With these biases accounted for, the method ofdetermining the center of rotation of the mechanical axis can be mademore accurate.

D. Additional Detail for Determining the Mechanical Axis

Provided below is additional detail that describes the methodologybehind the surgical orientation device 14 and/or reference device 16 andhow it is used to make certain calculations:

At least one purpose of the surgical orientation device 14 and/orreference device 16 and systems described herein is to provide guidanceto the surgeon as to how to position a cutting block on the bone inorder to achieve a cutting plane that is perpendicular to the loadbearing axis of the bone (or some number of degrees off of thatperpendicular plane if desired). A jig, such as that described above,can be fixed to the bone to be cut and the reference sensor device 16and surgical orientation device 14 can be attached to that jig (onedevice is attached to a fixed portion of the jig to act as a referenceto the bone's orientation and the other device is attached to anarticulating arm of the jig to provide the surgeon a means to find andset the desired cutting plane). The articulating arm of the jig can beconstrained to only be moved in two dimensions—pitch and yaw (notrotation). These two axes form a plane that can be adjusted to guide theplacement of the cutting block which guides the saw to cut the bone onthat plane.

Embodiments of a general approach can include determining the yaw (orvarus/valgus (V/V)) and pitch (extension/flexion) angles required tobring the surgical orientation device 14 and/or reference device 16 fromits initial orientation (provided by the other device, i.e. surgicalorientation device 14 and/or reference device 16) to its presentorientation.

In some embodiments, both sensors can begin aligned generally to thesame gravity vector (so that small angle assumptions apply). The presentorientation of the fixed sensor in the surgical orientation device 14and/or reference device 16 can be considered the initial orientation ofthe navigation sensor. The sensor in the surgical orientation device 14and/or reference device 16 can be free to move in pitch and yaw from theinitial orientation, but roll is considered fixed X,Y, and Z coordinateaxes for both sensors can be generally aligned. Both sensors can becalibrated with offset and gain and corrected for misalignment.

The surgical orientation device 14 and/or reference sensor device 16 canboth be 3 axis accelerometers and either one can play the role of afixed sensor. They can report the X, Y and Z components of the localgravity vector within the sensors coordinate system. For example, thefixed sensor can be the reference sensor device 16 and reports X1, Y1,Z1. The navigation sensor can be the surgical orientation device 14 Unitand reports X2, Y2, Z2.

At least one purpose of the system described herein is to provide anapparatus and method to determine the relative coordinates of a centerpivot point on a rigid linkage that overcomes the requirement for directphysical measurement. The acceleration and angular rate sensed by thesurgical orientation device 14 and/or reference device 16 can beprocessed while the link is moved by some means about its pivot point.The apparatus can provide an output vector representing the center ofthe linkage rotation with respect to the inertial sensor axes.

A method can start with the step of attaching the surgical orientationdevice 14 and/or reference device 16 to the linkage in a rigid manner.The data required from the surgical orientation device 14 and/orreference device 16 can be acceleration and angular rate. The data isinput to a microprocessor. In a preferred embodiment, the microprocessoris located on the link and output from the processor is transmitted viaRF wireless link, though this collocation is not a necessary condition.The link can be moved about its pivot point while inertial data is beingprocessed by the microprocessor. The algorithm implemented on themicroprocessor can process the inertial data in real time and determinesif the link is static or dynamically moving. Data from both states isused by the algorithm to determine the center of the link rotation. Thisresult is output by the microprocessor to the user.

The method and apparatus can provide accurate determination of pivotpoint location and radius of curvature without requiring any externalmeasurements. This allows determination of effective link pivot point inblind situations where the end joint is hidden or unobservable. Anexample of this is determination of the pivot point location a humanfemur. Below are formulae which are derived from basic centripetalacceleration physics coupled with optimal estimation or Kalman filteringtechniques to determine pivot point location.

The instantaneous translational velocity of a point on a rigid body isrelated to the link length and angular rate by

${\overset{\_}{R}}_{w} = {\overset{\_}{\omega} \times \overset{\_}{R}}$

Further, the translational velocity can be computed by integratingacceleration over the same time interval as shown here

$\mspace{85mu} {\text{?}\; = \; {{\text{?}\overset{\sim}{R}} + {\overset{\sim}{R}}_{0}}}$?indicates text missing or illegible when filed

Both of these can be further integrated into a position vector, R, whichrepresents the mechanical axis of the system, or the radial arm to thecenter of rotation. The unknown vector R is the key desired output fromthe apparatus. The vector R is found thru optimal estimation of thesystem. One cost function that can be used for estimation is

$l = {\frac{1}{2}e^{\tau}{We}}$

where e is the residual value computed from the difference between themeasured value and the expected values. For this method and apparatus,the measured value is the translational velocity and/or positiondetermined by integration of the accelerometer. The expected value isthe translational velocity and/or position determined by multiplying theestimated link vector by the measured angular rate data and the timeinterval across which that rate data is obtained in some cases. W is amatrix of weighting values that is typically all evenly weighted atunity.

One method is to vary an estimated vector, R, in such a way that thecost function is minimized.

There are many types of optimal estimator formulation. One can use aGauss-Newton in this description. Other methodology can also be used.Kalman filter estimators and other optimal (or even sub-optimal) methodsare valid also.

Prior to the final estimation, noise and error removal and reductionfrom the raw sensor data can be performed. This includes rate sensorbias, bias stability, angle random walk, scale factor errors andmechanical misalignments. Also included are accelerometer bias, biasstability, velocity random walk, scale factor errors and mechanicalmisalignments. Possible errors introduced by inaccurate removal ofgravitational influence are reduced. The amount of noise and errorremoval is proportional to the inherent capabilities of the sensors. Assensor technology gets better, certain portions of the algorithm may nolonger be needed to achieve the same accuracy.

There can be two modes to the operation of the system, data acquisitionand optimal estimation. During the data acquisition phase, data isacquired from the surgical orientation device 14 and/or reference device16 in a static condition, i.e. motionless. This static conditionprovides a baseline for the sensor and allows determination of biasesfor all internal sensors. The surgical orientation device 14 and/orreference device 16 is then moved by an operator or other means in sucha way that sufficient rate and acceleration data is achieved for allaxes. Lack of sufficient motion in any axes can reduce the effectivenessof the final output. During the data acquisition phase, the apparatuscan determine without user intervention what phase of data collection itis in, static or dynamic.

Correct inclusion of gravitation vector in the method can be importantfor accurate final results. Initial orientation of the surgicalorientation device 14 and/or reference device 16 during the static phaseof data acquisition is used to create an initial gravity vectortransformation matrix relating the orientation of the surgicalorientation device 14 and/or reference device 16 to the inertial gravityvector. Angular rate data can be used to propagate the attitude of theunit and update the inertial gravity vector transformation matrix duringsubsequent motion.

Once the data acquisition phase is determined to be complete, the secondphase, optimal estimation, is entered. This phase is further broken downinto three sub phases. These include gyro bias estimation, accelerometerbias estimation, and finally pivot point link vector estimation.

Some representative criteria for operation are now described thatprovide the most accurate pivot point estimation. During the static datacollection, at least 1 second, but no more than 3 seconds of data cannecessary in some embodiments. Longer periods of static data do notadversely affect the output. During the dynamic motion of the link,average angular rate in excess of 30 degrees per second are desiredBeginning and ending attitude of the link after dynamic motion iscomplete should be within 15 degrees on any axis in some embodiments.

The output pivot point center location, computed in an X,Y,Z vectorformat, can be transformed into relative 2 dimensional angles (e.g.pitch and yaw) representing the angular misalignment of the surgicalorientation device 14 and/or reference device 16 sensor axis withrespect to the mechanical line of action for the rigid link.

There can be 4 major phases to the overall method:

Data Acquisition and Pre-Scaling

Static biases are removed from the data and the average body framegravity vector is put back in the data

Optimal Estimation of Delta Theta (Rate Sensor) Bias

A bias is added to the rate sensor data in order to counter noise andother effects that result in the final orientation of the device beingmisaligned from the starting alignment, despite the fact that the useris required to return the unit back to the starting orientation.

Optimal Estimation of Delta Velocity (Accelerometer) Bias

A bias can be added to the accelerometer data in order to counter noiseand other effects that result in the final velocity of the device beingnon-zero.

Optimal Estimation of Femur Vector and Resolution into Angles

Below are mathematical bases for each section.

Data Acquisition and Pre-Scaling

The acquisition and pre-scaling required can be dependent on the sensorsselected for the device. One example of is described in the steps below.

Surgical orientation device 14 and/or reference device 16 raw data canbe acquired from a combination of accelerometers and rate sensors.

Data can be scaled into delta theta (radians) and delta velocity (cm/s)using the data sample rate. There are alternate formulations that maywork with the surgical orientation device 14 and/or reference device 16data natively, but this makes integration and other repeated functionsusing this data less computationally intense when implemented on amicroprocessor.

In some embodiments, the average of the raw data per each sensor andaxis during static conditions can be determined.

In some embodiments, the Direction Cosine Matrix required for level tocurrent orientation can be computed.

In some embodiments, the estimated average starting gravity vector inIMU body frame can be computed.

In some embodiments, the biases from all channels (rate andacceleration) can be removed.

In some embodiments, the body gravity vector can be added to theaccelerometer channels.

Optimal Estimation of Delta Theta Bias

The purpose of this step can be to determine the optimum rate sensorcorrections (in the form of a single constant bias for each sensor axis)that “force” the final attitude of the unit at the end of the maneuversto be identical to the starting attitude.

Let the matrix C_(i) ^(p) be the direction cosine matrix that representsthe rotation from the initial attitude (i) to the propagated attitude(p) at a given instant in time, t. C_(i) ^(p) includes the term Δ

, which is the rate sensor data from the IMU at each time step and Δ

a constant correction term. This final correction is determined in thefollowing steps to augment the data in an optimal fashion to ensure thatthe calculated final attitude matches the initial attitude despitenoises and other errors that alter the propagation from the correctsolution.

Let p be the equivalent set of Euler angles that represent the singlerotation from the initial attitude to the current attitude representedby C_(i) ^(p).

The surgeon can move the surgical orientation device 14 and/or referencedevice 16 in a prescribed set of motions and return the unit back to thestarting attitude. The assumption is that sensor noises will result inan incorrect attitude at the end of the motions. Using Gauss-Newton orany variety of similar optimal estimation algorithm, the

terms will be determined that minimize the attitude error cost function.

For determination of Δ

terms, we define the cost function as:

$\overset{\_}{l} = {{\overset{\_}{p}}_{initial} - {\overset{\_}{p}}_{final}}$

This cost function can be minimized by altering the Δ

terms according to an optimal estimation algorithm. We present aGauss-Newton approach here, though other equivalent approaches are alsoappropriate.

Given a loss function, J, evaluated at a local pointx _(i), we want tomodify x _(i) by Δx _(i) as:

=x _(i)+≢x _(i), so that J is decreased. Standard texts and referencesshow methods to solve this problem.

Using a Gauss Newton algorithm to solve this problem, we substitute Ī=

for the loss function with

=0 by definition, and x _(i)=Δ

.

FIG. 50C is a flow chart for calculations and operations shows theprocedure that is used to iteratively solve for the optimal value of Δ

.

The output result is a set of data that represents the change in angularrotation based on corrected rate sensor data.

Optimal Estimation of Delta Velocity Bias

The purpose of this step is to determine the optimum accelerometersensor corrections (in the form of a single constant bias for eachsensor axis) that “force” the final velocity of the unit at the end ofthe maneuvers to be identical to the starting velocity based onintegrated acceleration data.

This approach can be augmented to include an additional constraint thatthe starting and stopping positions must be identical as well.

Let the matrix C_(i) ^(p) be the direction cosine matrix that representsthe rotation from the initial position (i) to the propagated position(p) at a given instant in time. This has been presented previously.

This rotation matrix is applied to the accelerometer data and acorrection term (ΔV

_() to transform it into the inertial reference frame.)

The surgeon can move the unit in a prescribed set of motions and returnthe unit back to the starting position. The assumption is that sensornoises will result in an incorrect velocity at the end of the motions.Using Gauss-Newton or similar optimal estimation algorithm, the ΔV

_(terms will be determined that minimize a representative velocity error cost function.)

For determination of ΔV _(terms, we define the cost function as:)

$\overset{\_}{l} = {{\overset{\_}{V}}_{initial} - {\overset{\_}{V}}_{final}}$

This cost function can be minimized by altering the ΔV

_(terms according to an optimal estimation algorithm.)

We do not repeat the procedure here, but the prior Gauss-Newton flowchart is applicable to this estimator.

The output result is a set of data that represents the change inposition in the inertial frame of the IMU based on the accelerometerdata.

Optimal Estimation of Femur Vector

The purpose of this step is to determine the optimum vector from thesurgical orientation device 14 and/or reference device 16 frame to itsrigid body center of rotation. The accelerometer sensor data provides alinear acceleration estimate of velocity and motion. In a similarmanner, the rate sensors on the surgical orientation device 14 and/orreference device 16 will provide estimates of position and motion if therigid vector to the unit is known.

The accelerometer data provides a position vector at each time step R

_(The creation of this data set has been detailed.)

The rate sensor data can provide a position vector at each time step perthe equation:

     ?(t) = Δ?(t) × ??indicates text missing or illegible when filed

For determination of R

_(terms, we define the cost function as:)

$\mspace{79mu} {\overset{\_}{l} = {\text{?} - \text{?}}}$?indicates text missing or illegible when filed

This cost function can be minimized by altering the R

_(terms according to an optimal estimation algorithm.)

We do not repeat the procedure here, but the prior Gauss-Newton flowchart is applicable to this estimator.

To use the previous method, we substitute Ī=R _(a)−R _(g) for the lossfunction with R

an unchanging dataset created previously and R _(g) created thru thecross product of the Δ

_(e) data set and the current estimated vector.

The output result is an optimal estimation of the vector from the IMU tothe center of the rotation, R

_(.)

This vector is located in the body frame of the IMU.

Angles in pitch and yaw to the center of the joint can be computed basedon this vector.

E. Adjusting an Angle of Resection

Once biases have been removed, and the reference sensor device 16 and/orsurgical orientation device 14 has calculated the pivot point of themechanical axis as described above and located the mechanical axis, theuser can begin adjusting and orienting the cutting block 92 relative tothe location of the mechanical axis. For example, the surgicalorientation device 14 can display the varus/valgus and flexion/extensionangle adjustments needed for the surgical orientation device 14 (and thefemoral jig assembly 12) to reach neutral alignment with the mechanicalaxis that passes through the femoral head 154.

Advantageously, in some embodiments the reference sensor device 16 canenable the procedure to proceed without fixation of the leg beingoperated upon because the reference sensor device 16 can track therelative positions of the leg. For example, at least one of thereference sensor device 16 and the surgical orientation device 14 cancommunicate with the other, such that any relative movement of one ofthe devices can be tracked by the other, and the resulting overallorientation of the reference sensor device 16 and/or surgicalorientation device 14 can be displayed on display 26 of the surgicalorientation device 14. In some embodiments, the reference sensor device16 can track movement of the leg (i.e. femur or tibia), such that if theleg moves during a procedure, the overall orientation of the surgicalorientation device 14 can remain accurate.

With continued reference to FIGS. 22-31, a femoral preparation methodcan comprise placing the leg back into a flexion position (similar tothe position shown in FIG. 22) and using varus/valgus andflexion/extension angle adjustment information provided by the surgicalorientation device 14 in order to adjust an intended angle(s) ofresection. The varus/valgus and flexion/extension angle adjustments ofthe femoral jig assembly 12 can be made by the translation structures120 discussed above (e.g., by turning each of the translation adjustmentfeatures 130 in a clockwise or counter-clockwise position, and readingthe resulting change in orientation on the display 26 of the surgicalorientation device 14).

Any varus/valgus and flexion/extension angle adjustments of the femoraljig assembly 12 made by the adjusting the translation adjustmentfeatures 130 as discussed above can be reflected and displayed inapproximately real time by the surgical orientation device 14. Thevarus/valgus and flexion/extension angle adjustments of the femoral jigassembly 12 can be made until the user is satisfied with thevarus/valgus and flexion/extension angles of the femoral jig assembly 12being reflected and displayed by the surgical orientation device 14. Insome embodiments, when the surgical orientation device 14 and thefemoral jig assembly 12 are aligned with the mechanical axis, thesurgical orientation device 14 can provide a signal, such as for examplea flashing green light on its display 26.

Furthermore, the surgical orientation device 14 can provide anindication of degrees of movement. For example, the surgical orientationdevice 14 can inform the user how many degrees (e.g. in half degreeincrements) the surgical orientation device 14 and the femoral jigassembly 12 are rotated past the mechanical axis of the leg in one ormore planes. The surgical orientation device 14 can display thisinformation in its display 26, and/or provide audio indications to theuser.

After the femoral jig assembly 12 is aligned with the femoral mechanicalaxis and/or the cutting angles are selected, the method can includeattaching the cutting block 92 and the distal guide assembly 88 to themicroblock assembly 90 of the femoral jig assembly 12 as shown in FIG.28. The cutting block 92, distal guide assembly 88, and microblockassembly 90 can be coupled, e.g., attached to each other or coupledindependently to the femur. In most cases, the distal guide assembly 88will have moved from the original position illustrated in FIG. 22, sothe pin 102 would not necessarily line up with the hole created asdiscussed in connection with FIG. 22. In these cases, cutting block 92,distal guide assembly 88, and microblock assembly 90 can be coupled byconnecting the articulating arm 98 with the microblock assembly 90 andthe cutting block 92 via the attachment features 122 and the receivingfeatures 136. If at this point of the procedure the distal guideassembly 88 is in the original position, the pin 102 also can beinserted back into the hole 146 to aid in coupling the cutting block 92,distal guide assembly 88, and microblock assembly 90.

As discussed above, the distal femoral resection depth can be set bymoving the articulating arm 98 in a desired position in relation to thecutting block 92 by adjusting the position adjustment features 104.

Referring to FIGS. 29 and 30, the femoral jig assembly 12 optionally caninclude an alignment rod 156 if the user desires to confirm alignment byreferencing the anterior superior iliac spine visually. The optionalalignment rod 154 can be attached to different parts of the femoral jigassembly 12 such as to one of the attachment features 122 of themicroblock assembly 90 or one of the receiving features 136 or openingin the cutting block 92. Two exemplary embodiments of the optionalalignment rod 156 are shown in FIGS. 29 and 30.

Referring to FIG. 31, the femoral preparation method can includeimmobilizing the cutting block 92 at the femoral resection location byinserting positional pins 158 into the appropriate receiving features136. Any number of positional pins 158 (e.g., 2 or more) can be insertedinto the appropriate receiving features 136. Except for the cuttingblock 92 immobilized at the femoral resection location by the positionalpins 158, all other components of the femoral preparation system 10 suchas the surgical orientation device 14, the reference sensor device 16,the first coupling device 18, the second coupling device 20, the distalguide assembly 88 and the microblock assembly 90 can all be disconnectedand removed during this stage of the method as shown in FIG. 31.

The method can further include using the cutting block 92 to perform thedesired distal femoral resection using standard methods. For example, acutting tool or tools can be moved through the at least one opening 134of the cutting block 58, so as to prepare the distal femur for receivinga knee joint prosthetic. After a distal femoral resection is completedin accordance with the method described above, the proximal (i.e. upper)tibia can then be resected.

IV. Alternative Embodiments of Femoral Jig Assembly/method

Referring to FIGS. 31A-C, an alternative embodiment of a femoral jigassembly 12′ can comprise an orthopedic assembly for femoral preparationduring a total knee replacement procedure. The jig assembly 12′ providesthree point connection to a bone to enhance stability. Although the jig12 allows as many as six microblock pins 152 to be inserted into thefemur and thus provide a stable configuration, an arrangement thatprovides a pin location that is spaced away from the location of thepins 152 can provide a triangular pin arrangement, which is much morestable and less prone to rocking.

The femoral jig assembly 12′ can be similar to the femoral jig assembly12 described above, and have similar components. For example, thefemoral jig assembly 12′ can comprise a distal guide assembly 88′, amicroblock assembly 90′, and a cutting block 92′.

The distal guide assembly 88′ can comprise a modular paddle 96′, anarticulating arm 98′, and a midline pin 102′. The modular paddle 96′ cancomprise an extension 97′. As used in this specification, the term“modular paddle” or more generally “modular” includes structures thatcan form part of a kit, for example, of selectable parts. Various otherkits, including any combination of the components described herein, canalso be used or implemented in accordance with the methods describedherein. The extension 97′ can comprise, for example, a generallyL-shaped structure having a slot 99′ for receiving or for facilitatingmovement of the articulating arm 98′. The extension 97′ can comprise amarking or markings (not shown), similar to the markings 108 on thepaddle 96 described above, for indicating an AP offset. For example, aseries of lines can be provided along the slot 99′ such as on one ormore of the distal, lateral, or medial surfaces of the extension 97′.These lines can be used to collect AP Offset Data, as discussed above toenable one or more orientation or reference devices coupled with thefemoral jig assembly 12′ to account for the offset from the midline pin102′ and the orientation or reference device.

The articulating arm 98′ can comprise or be coupled with a grippingstructure 101′ located on an end of the articulating arm 98′ thatextends through the slot 99′. The gripping structure 101′ can beconfigured to be gripped by a user's hand or fingers and moved, alongwith the rest of articulating arm 98′, in an anterior/posteriordirection (see, e.g. FIGS. 31B and 31C showing a change in position ofthe articulating arm 98′ from posterior to anterior). The articulatingarm 98′ can extend through the slot 99′, and through, for example, asleeve 103′ located within the microblock assembly 90′. As illustratedin FIGS. 31B and 31C, the sleeve 103′ can form part of a sliding member105′ that sits within the microblock assembly 90′ (e.g. within groovesof a member 118′). Thus, when the gripping structure 101′ is held andmoved in an anterior/posterior direction, the articulating arm 98′,sleeve 103′, and 105′ move as well. The cutting block 92′ can rest on orbe attached to the articulating arm 98′, such that movement of thegripping structure 101′ additionally causes anterior/posterior movementof the cutting block 92′, moving the cutting block 92′ closer to thecondyles of the femur when ready for resection. This advantageouslyallows the cutting block 92′ to be moved close to the femur, making iteasier to insert pins and secure the cutting block when needed.

The microblock assembly 90′ can comprise a microblock member 116′ thatincludes a stabilizing bar 107′. The stabilizing bar 107′ can be formedintegrally with or attached to the microblock member 116′. In otherembodiments, the stabilizing bar 107′ can be integrally formed with orattached to the distal guide assembly 88′. The stabilizing bar 107′ canbe used to help anchor and/or secure the jig assembly 12′ to the femurby providing a third anchoring location. For example, the microblockmember 116′ can comprise openings 132′ on either side of the microblockmember 116′ (e.g. medial and lateral) for receiving pins. Thestabilizing bar 107′ enhances stability of the microblock member 116′provided by the two openings 132′ to further reduce rotational movementof the jig assembly 12′ about an axis extending between the two openings132′ on either side of the microblock member 116′. The stabilizing bar107′ can be used to provide a third anchoring point, completing atriangular array of anchoring points (e.g., medial and lateral of ananterior- posterior mid-plane, adjacent to the condyles and proximal ofthe condyles) along the femur that add stability to the jig assembly12′. In the illustrated embodiment, two anchor locations can be disposeddistally of the cutting block 92′ and one can be positioned proximallythereof. For example, the stabilizing bar 107′ can extend around oneside of the microblock assembly 90′ (i.e. depending on how the kneeanatomy is structured and/or moved during a procedure). In someembodiments, the stabilizing bar 107′ can project posteriorly to attachto the distal femur (e.g. to the back side of the femur, or to a ledge,condyle, plateau or side of the femur). In one technique, during theprocedure the patella is displaced to a lateral side of the knee jointand the stabilizing bar 107′ is coupled with and extends from a portionof the microblock assembly 90′ that will be disposed on a medial side ofthe knee joint during the procedure. The stabilizing bar 107′ cancomprise a pin tube 109′ with an opening 111′ for receiving a pin (notshown) that extends through the femur and helps to anchor the jigassembly 12′ in place.

As discussed elsewhere herein, a variation on the femoral jig assembly12′ enables procedures that do not require collecting AP offset data.For example, the arm 98′ can be configured not to be moveable, e.g., tobe in a fixed anterior-posterior location relates to the midline pin102′ during at least one phase of the procedure. In the embodiment ofFIGS. 31A-31C, positioning of the cutting block 92′ is facilitated bythe movement of the arm 98′. If the arm 98′ is fixed, the block 92′ canbe mounted on a separate mechanism that is moveable in theanterior-posterior direction to facilitate positioning the block 92′away from the femur at one point of a procedure and up adjacent to thefemur in another phase.

Referring to FIGS. 31D-F, another alternative embodiment of a femoraljig assembly 12″ can comprise an orthopedic assembly for femoralpreparation during a total knee replacement procedure. The jig assembly12″ can include similar components to those described above. Forexample, the jig assembly 12″ can include a microblock assembly 90″,cutting block 92″, translating member 118″, translation structures 120″,and attachment features 122″. In some embodiments, a surgicalorientation device 14 and/or reference sensor device 16 can be attachedto attachment features 122″ of femoral jig assembly 12″.

With continued reference to FIGS. 31D-F, in some embodiments the femoraljig assembly 12″ can include a microblock assembly 90″ that includes anintegrated distal guide 96″, which provides a function similar to thatof the paddle 96 described above. The distal guide 96″ can be configuredto extend over and press against one or more of the distal condyles 148of a knee bone, such as a femur. The distal guide 96″ can be integrallyformed with the microblock assembly 90″. The distal guide 96″ providesadvantages over the paddle 96 by integrating the functions of a separatedistal guide component with a microblock assembly that is alreadyrigidly attached to the distal femur. Fewer separate components can beused, thus making the overall jig assembly 12″ and method of using thejig 12″ more efficient. In some embodiments, a separate articulating arm98″ can extend through the microblock assembly 90″, as well as throughthe cutting block 92″.

The jig assembly 12″ can also include a midline guide 100″. The midlineguide 100″ can be similar to midline guide 100 shown in FIG. 18. Forexample, the midline guide 100″ can be moved relative to the distalguide 96″ within a channel 106″. The midline guide 100″ can include oneor more guide markings 108″, and the distal guide 96″ can include one ormore distal guide markings 113″. The midline guide markings 108″ anddistal guide markings 113″ can be used to determine a relative offset ofthe microblock assembly 90″, and/or cutting block 92″, relative to afixed location. For example, the midline guide markings 108″ and paddlemarkings 113″ can be used to determine an anterior/posterior offset ofthe cutting block 92″, surgical orientation device 14, or referencesensor device 16 relative to a mechanical axis extending through thefemur. Such an offset can be entered, for example, into the surgicalorientation device 14 or reference sensor device 16.

With continued reference to FIGS. 31D-F, the midline guide 100″ caninclude at least one pin mounting structure 115″. In some embodiments,the pin mounting structure 115″ can comprise a threaded structure. Thepin mounting structure 115″ can be configured to receive at least onepin or other mounting feature. For example, the pin mounting structure115″ can include an opening 117″. The opening 117″ can be configured toreceive a mounting pin. The mounting pin can be inserted into and canextend through the opening 117″, and into the distal end of a femur.Once the pin is inserted into a distal end of the femur, the midlineguide 100″ can be fixed in place, and the microblock assembly 90″ can bemoved relative the midline guide 100″, for example in ananterior/posterior direction, to adjust a position of the cutting block92″.

Yet even further embodiments of femoral jig assemblies and methods fortheir use, as well as methods for determining a center of rotation of ahead of the femur, can be found in, for example without limitation,paragraphs [305]-[333] and FIGS. 5 and 40-43 of U.S. patent applicationSer. No. 12/509,388, which is incorporated by reference herein.

V. Testing of the Embodiments of the Invention

Embodiments of the invention similar to those described herein haverecently been tested. In a comparison with a commercially available,FDA-cleared optical-based computer-assisted surgery system currentlyused in the United States operating rooms, 20 mechanical tibialmechanical axis registrations were conducted on 4 cadaver legs and 30femoral mechanical axis registrations were conducted on 5 cadaver legsusing each of an embodiment of the invention and the standardoptical-based computer-assisted surgery system. (See tables below;registrations labeled N/A were not taken into account because they didnot meet test criteria) The average difference between the distalfemoral cutting block mechanical axis orientation calculated by theembodiment of the invention and that calculated by the optical-basedcomputer assisted surgery system was no more than 1 degree for bothvarus/valgus and flexion/extension angles. Similarly, the averagedifference between the tibial cutting block mechanical axis orientationcalculated by the embodiment of the invention and that calculated by thecommercially-available optical-based computer assisted surgery systemwas no more than 1 degree for both varus/valgus and posterior slopeangles. These results provide acceptable performance in a very compactand simple to use system. Also, these excellent results are produced bymuch less costly devices.

TABLE 1 FEMORAL Computer Assisted KneeAlign 2 System Deviation VarusFlex Varus Flex Varus Flex (+)/ (+)/ (+)/ (+)/ (+)/ (+)/ Regis- ValgusExten Valgus Exten Valgus Exten Femur tration (−) (−) (−) (−) (−) (−) 11 N/A N/A N/A N/A N/A N/A 2 N/A N/A N/A N/A N/A N/A 3 N/A N/A N/A N/AN/A N/A 4 N/A N/A N/A N/A N/A N/A 5 0 0 1.0 −1.0 −1.0 1.0 6 0 0 0.5 −1.0−0.5 1.0 7 0 0 0.5 −1.0 −0.5 1.0 8 0 0 0.5 0.0 −0.5 0.0 9 0 0 −0.5 0.00.5 0.0 2 1 −2 3 −3.5 3.5 1.5 −0.5 2 −2 3 −3.5 2.5 1.5 0.5 3 −2 3 −3.5 31.5 0 4 −2 3 −2 3 0 0 5 −2 3 −3 2.5 1 0.5 3 1 2 3 0.5 3 1.5 0 2 2 3 11.5 1 1.5 3 2 3 0.5 0.5 1.5 2.5 4 2 3 3 3 −1 0 5 2 3 1 0.5 1 2.5 6 2 3 21 0 2 7 2 3 0.5 0.5 1.5 2.5 4 1 N/A N/A N/A N/A N/A N/A 2 N/A N/A N/AN/A N/A N/A 3 0 5 −1.5 3.5 1.5 1.5 4 0 5 0.5 3.5 −0.5 1.5 5 0 3 2 6 −2−3 6 0 0 1.5 0.5 −1.5 −0.5 7 0 0 1.5 0 −1.5 0 8 0 0 0 0 0 0 9 0 0 0 0.50 −0.5 10 0 0 1 1 −1 −1 5 1 0 5 0 3 0 2 2 0 5 0.5 3.5 −0.5 1.5 3 0 5 04.5 0 0.5 4 0 5 0 4.5 0 0.5 5 0 5 0 4 0 1 Mean 0.0 0.6 Stdev 1.09 1.17Max 2.00 3.00

TABLE 2 TIBIAL Computer Assisted KneeAlign 2 System Deviation Varus FlexVarus Flex Varus Flex (+)/ (+)/ (+)/ (+)/ (+)/ (+)/ Regis- Valgus ExtenValgus Exten Valgus Exten Tibia tration (−) (−) (−) (−) (−) (−) 2 1 0 31.0 3.5 −1.0 −0.5 2 0 3 0.0 3.5 0.0 −0.5 3 0 3 −0.5 2.5 0.5 0.5 4 0 30.0 3.5 0.0 −0.5 5 0 3 0.0 3.0 0.0 0.0 3 1 2 5 0 6.5 2.0 −1.5 2 2 5 0.56.5 1.5 −1.5 3 2 5 1 7 1.0 −2.0 4 2 5 2 5 0.0 0.0 5 2 5 1 6.5 1.0 −1.5 41 0 7 −1 9 1.0 −2.0 2 0 7 −1 9 1.0 −2.0 3 0 7 −0.5 8 0.5 −1.0 4 0 7 0 80.0 −1.0 5 0 7 −0.5 7.5 0.5 −0.5 5 1 0 7 0 8 0.0 −1.0 2 0.5 7 2.5 7.5−2.0 −0.5 3 0 7 1.5 9.5 −1.5 −2.5 4 0 7 1 6 −1.0 1.0 5 0 7 0.5 9 −0.5−2.0 Mean 0.2 −1.0 Stdev 1.00 0.93 Max 2.00 2.5

VI. User Interfaces for Femoral Preparation Methods

As discussed above, various components such as the electronic controlunit 1102, the user input 26 and the display 26 of the surgicalorientation device 14 can form an interactive user interface. Theinteractive user interface can include a graphical user interface havingan interactive window displaying on-screen graphics on the surgicalorientation device 14. The interactive user interface can provide theuser with a plurality of screen displays illustrating steps to beperformed in a surgical procedure and can guide the user through theperformance of the steps. Each screen display can comprise one or moreon-screen graphics. The on-screen graphics can comprise one or morevisual cues or indicators to prompt the user as to what step or steps totake next during one of the procedural methods described above.

The visual cues referenced herein can comprise instructive images,diagrams, pictorial representations, icons, animations, visual cues,charts, numerical readings, measurements, textual instructions, warnings(visual and/or audible), or other data. The interactive user interfacecan be configured to alter attributes (e.g., color) of the on-screengraphics according to one or more data protocols. The interactive userinterface can provide visual feedback to the user during performance ofone or more surgical procedures. The interactive user interface can beconfigured to generate GUI images to be displayed to the user. Asdescribed above, the user can interact with the surgical orientationdevice 14 via one or more user input devices 1114 (e.g., buttons,switches, touch screen displays, scroll wheel, track ball, keyboard,remote controls, a microphone in conjunction with speech recognitionsoftware). The interactive user interface can further allow a user toconfirm that a step has been completed (for example, by pressing a userinput button). The interactive user interface can allow the user toenter data (e.g., a numerical value, such as a distance, an angle,and/or the like), verify a position of the surgical orientation device14, turn an optional visible alignment indication system on and off,and/or turn the entire surgical orientation device 14 on and off.

In certain embodiments, the interactive user interface can provide oneor more drop-down lists or menus from which a user can make selections.For example, the user can make selections from a drop-down list using ascroll wheel, trackball, and/or a series of button presses. In someembodiments, the user interface provides a drop-down list of predicatesthat dynamically updates based on user input.

In at least one embodiment, a module for creating an interactive userinterface can comprise a computer readable medium having computerreadable program code embodied therein. The computer readable programcode can include computer readable program code configured to displayone or more of a plurality of GUI images on the user interface of thesurgical orientation device 14, the GUI images comprising instructiveimages related to the performance of a surgical procedure. The computerreadable program code can be configured to receive instructions from auser identifying the surgical procedure to be performed. The computerreadable program code can be configured to show the user steps to beperformed in the identified process for the identified surgicalprocedure. The computer readable program code can be configured to guidethe user in performance of the steps. For example, the computer readableprogram code can be configured to receive from the user an instructionto continue to the next step in the procedure, to receive orientationdata from a sensor mounted within the surgical orientation device, andto display the orientation data on the user interface of the surgicalorientation device.

In at least one embodiment, the surgical orientation device 14 caninclude a display module configured to display information and at leastone sensor module configured to monitor the position and orientation ofthe surgical orientation device 14 and the reference sensor device 16 ina three-dimensional coordinate reference system, and to generateorientation data corresponding to the monitored positions andorientations of the surgical orientation device 14 and the referencesensor device 16.

The surgical orientation device 14 can further comprise a control moduleconfigured to receive orientation data from the at least one sensormodule and convert it to objective signals for presentation on a displaymodule. The control module can be configured to display a set of GUIimages or other on-screen graphics on the display module, the GUI imagesor on-screen graphics representing the orientation data received fromthe sensor module and also representing instructive images related tothe performance of the joint replacement surgery.

In at least one embodiment, the surgical orientation device 14 canreceive orientation data from a sensor module, receive input commandsfrom a user input module to store orientation data from a user inputmodule, convert the orientation data to a human readable format forpresentation on a display device, and display on the display deviceon-screen graphics or GUI images for communicating information to a userbased on the input commands and the orientation data, the informationcomprising instructive images for performing a joint replacement surgeryand one or more visual indicators of a current orientation of thedisplay device with respect to a fiducial, or reference, orientation.

FIGS. 32A-J display exemplary screen shots that can be displayed by theinteractive user interface of the surgical orientation device 14 (e.g.displayed on an LCD screen on the front of the surgical orientationdevice 14) during the various steps of an orthopedic procedure.

For example, FIG. 32A displays a screen shot that provides a visual cueinforming the user that the knee being operated on is to be placed in aflexion position and that the femoral jig assembly 12 should be attachedto the distal end portion of the knee.

FIG. 32B displays a screen shot that provides a visual cue informing theuser to enter an AP Offset Data. The image in FIG. 32B can be displayedin response to pressing a user input button 28 specified by the surgicalorientation device 14 in FIG. 32A. In another embodiment, and asdescribed above, the process of obtaining and entering AP Offset Datainto the surgical orientation device 14 can be avoided if a fixed offsetdistance is provided by the configuration of the femoral preparationsystem 10.

FIG. 32C displays a screen shot that provides a visual cue informing theuser to perform a removal step of the method described above. The imagein FIG. 32C can be displayed in response to pressing a user input 28button specified by the surgical orientation device 14 in FIG. 32B.

FIG. 32D displays a screen shot that provides a visual cue informing theuser to perform installation and leg extension placement steps of themethod described above. The image in FIG. 32D can be displayed inresponse to pressing a user input button 28 specified by the surgicalorientation device 14 in FIG. 32C.

FIG. 32E displays a screen shot that provides a visual cue informing theuser to perform a 30 degree abduction step. The image in FIG. 32E can bedisplayed in response to pressing a user input button 28 specified bythe surgical orientation device shown in FIG. 32D.

FIG. 32F displays a screen shot that provides a visual cue informing theuser to perform a 30 degree raising leg step. The image in FIG. 32F canbe displayed in response to pressing a user input button 28 specified bythe surgical orientation device 14 in FIG. 32E. Alternatively, it ispossible to change the sequence so that FIG. 32F is displayed inresponse to pressing the user input button 28 specified by the surgicalorientation device 14 in FIG. 32D and FIG. 32E is displayed in responseto pressing the user input button 28 specified by the surgicalorientation device in FIG. 32F.

FIG. 32G is a screen shot that provides a visual cue informing the userof angle adjustments (e.g. varus/valgus and flexion/extension angleadjustments) needed for the surgical orientation device 12 and thefemoral jig assembly 12 to reach neutral alignment with the mechanicalaxis. The image in FIG. 32G can be displayed in response to pressing auser input button 28 specified by the surgical orientation device 14 inFIG. 32F.

FIG. 32H displays a screen shot that provides a visual cue informing theuser how to perform angle adjustments (e.g. varus/valgus andflexion/extension angle adjustments) of the translating member 118 byusing the translation structures 120. FIG. 32H can be displayed inresponse to pressing a user input button 28 specified by the surgicalorientation device 14 in FIG. 32G.

FIG. 32I displays a screen shot that provides a visual cue informing theuser to perform a femoral resection depth adjustment step. The image inFIG. 32I can be displayed in response to pressing a user input button 28specified by the surgical orientation device 14 shown in FIG. 32H. Atthis step, the cutting block 92, which can be attached to the microblockassembly 90, can be at a desired location aligned with the mechanicalaxis for distal femoral resection.

FIG. 32J displays a screen shot that provides a visual cue informing theuser to perform a tibial preparation method. The image in FIG. 32J canbe displayed in response to pressing a user input button 28 specified bythe surgical orientation device 14 shown in FIG. 32H. In someembodiments, the display 26 of the interactive user interface can beconfigured to automatically shut off after the femoral procedure iscompleted, rather than moving directly to the tibial preparation.

Further embodiments of user interfaces, for use for example in anorthopedic method, can be found in paragraphs [0377]-[430] and FIGS.58A-61K of U.S. patent application Ser. No. 12/509,388, which isincorporated by reference herein.

VII. Tibial Preparation Systems

Referring to FIG. 33, a tibial preparation system 210 can be used formodifying a natural tibia with a proximal tibial resection to enable aprosthetic component to be securely mounted upon the proximal end of thetibia. The tibial preparation system 210 can comprise, for example, atibial jig assembly 212, a landmark acquisition assembly 214, a surgicalorientation device 14 (e.g. the surgical orientation device describedabove), and a reference sensor device 16 (e.g. the reference sensordevice described above).

A. Orthopedic Assembly for Angular Adjustment

The tibial jig assembly 212 can comprise an orthopedic assembly for usein preparing a tibia for a prosthetic component, and in particular formaking angular adjustments relative to an anatomical feature. Referringto FIGS. 34-38, the tibial jig assembly 212 can comprise for example oneor more of a posterior slope assembly 216, a varus-valgus assembly 218,and a mounting bar assembly 220. The tibial jig assembly 212 can beconfigured to be coupled with one or more additional components. Forexample, the tibial jig assembly 212 can be coupled with a stylusresection guide 222, a tibial cutting block assembly 224, and/or amidline probe assembly 226, as illustrated in FIGS. 43, 44A-B, and45A-C, respectively.

Referring to FIGS. 34 and 38, the tibial jig assembly 212 can include areference sensor device interface 228 by which the reference sensordevice 16 can be coupled to the tibial jig assembly 212, and a surgicalorientation device interface 230 by which the surgical orientationdevice 14 can be coupled to the tibial jig assembly 212. The referencesensor device 16 can preferably be coupled with the tibial jig assembly212 such that during a total knee replacement procedure, the referencesensor device 16 follows the movement of the tibia, and generally doesnot move independently with respect to the tibia. In some embodiments,reference sensor device interface 228 can comprise a plurality of postsdisposed on a side surface of the mounting bar assembly 220 forconnecting with the reference sensor device 16. The configuration of thereference sensor device interface 228 can enable low profile mounting ofthe reference sensor device 16 beneath other components of the tibialjig assembly 212, such that the reference sensor device 16 can belocated between at least one moving component of the tibial jig assembly212 and the tibia of the patient.

In a preferred arrangement, the orientation device interface 230 and thereference sensor device interface 228 can be coupled with portions ofthe tibial jig assembly 212 that are capable of moving relative to eachother. For example, the orientation device interface 230 can be disposedon a movable portion of the tibial jig assembly 212, such as theposterior slope assembly 216, whereas the reference sensor deviceinterface 228 can be disposed on a generally stationary portion of thetibial jig assembly 212, such as the mounting bar assembly 220.

1. Device for Adjusting a Posterior/Anterior Slope of a Cutting Block

In a preferred arrangement, the tibial jig assembly 212 can comprise acomponent for adjusting a posterior/anterior slope of the surgicalorientation device 14 and/or a cutting block. For example, as seen inFIGS. 34-38, and 40A-B, the tibial jig assembly 212 can comprise aposterior slope assembly 216 that is adjustable in a posterior andanterior direction relative to the mounting bar assembly 220. Withreference to FIG. 38, the posterior slope assembly 216 can comprise anelongate posterior slope arm 232, a posterior slope cam 234, a washer236, a first posterior slope cam pin 238, a second posterior slope campin 240, a posterior slope opening (e.g. slot) 242, and a posteriorslope pivot arm 244.

2. Device for Adjusting a Varus/Valgus Slope of a Cutting Block

In a preferred arrangement, the tibial jig assembly 212 can alsocomprise a component for adjusting the varus/valgus slope of a cuttingblock. For example, as seen in FIGS. 34-38, the tibial jig assembly 212can comprise a varus/valgus assembly 218 that is adjustable in a varusand valgus direction. With reference to FIG. 38, the varus-valgusassembly 218 can comprise an elongate varus-valgus arm 246, an opening248 to receive the posterior slope pivot arm 244, a varus-valgus camassembly 250, a varus-valgus cam pin 252, a varus-valgus slide opening254, a posterior pivot pin 256, a varus-valgus pivot pin 258, an opening260 to receive the varus-valgus pivot pin 258, a posterior pivot pin262, and an opening 264 to receive at least a portion of the elongatearm 232 described above.

3. Device for Securing an Orthopedic Fixture Against the Tibia

In a preferred arrangement, the tibial jig assembly 212 can alsocomprise a device for securing an orthopedic fixture against the tibia.For example, as seen in FIGS. 34-39B, in some embodiments the tibial jigassembly 212 can comprise a mounting bar assembly 220 that is configuredto be secured (e.g. anchored) to a tibia. The mounting bar assembly 220can comprise a mounting bar 266 configured to rest against the lower legor tibia. The mounting bar 266 can have a generally v-shaped formation,or any other formation that facilitates alignment and/or placementagainst a lower leg. The mounting bar assembly 220 can further comprisean elongate mounting bar arm 268, a pivot guide member 270 configured toextend within the varus-valgus slide opening 254 described above, anopening 272 configured to receive the varus-valgus pivot pin 258described above, a rotation pin washer 274, and a bone rest 276. Asillustrated in FIG. 39B, the bone rest 276 can comprise a rotation pin278, anchor spring 280, and rotation pin washer 282 that permits thebone rest 276 to be rotated 180 degrees (e.g. to be used on a left legas opposed to a right leg and vice versa). As illustrated in FIG. 39B,the pivot guide member 270 can further comprise at least onevarus-valgus stop pin 284 to limit the rotational movement of the tibialjig assembly 212 described above. The bone rest 276 can be optional. Forexample, FIGS. 50A-50B show a variation of the tibial preparation systemthat couples a proximal portion thereof with a tibial plateau instead ofwith an anterior face of the tibia. The embodiment of FIGS. 50A-50B isadvantageous at least in that it eliminates the need for drilling holesin the anterior face of the tibia for mounting the bone rest 276.

Secure engagement of the mount bar assembly 220 with the lower leg ofthe patient can be enhanced by providing a spring (not shown) that, inuse, wraps around the posterior side of the leg and couples to medialand lateral sides of the mounting bar 266. The spring can be secured totabs 286 of the mounting bar 266 seen in FIG. 38. The spring can also bea tension member or another form of biasing member.

As illustrated in FIGS. 34-36, the components of the tibial jig assembly212 can be adjusted and moved relative to one another. For example, FIG.34 is a perspective view of the tibial jig assembly 212 with theposterior slope assembly 216 at a generally neutral position. In FIG.34, the varus-valgus assembly 218 is also in a neutral position. As usedherein the “neutral position” is a broad term that includes any positionin which a selected portion of the tibial jig assembly 212 or componentsassociated therewith is parallel to or in a common plane with amechanical axis or other relevant axis of the knee joint.

FIG. 35 is a perspective view of the tibial jig assembly 212 of FIG. 34,with the posterior slope assembly 216 out of the neutral positionproviding an anterior to posterior slope adjacent a proximal end of thetibial jig assembly 212. Such a slope can correspond to an anterior toposterior slope for a cutting block.

FIG. 36 is a perspective view of the tibial jig assembly 212 of FIG. 34,with both the posterior slope assembly 216 and the varus-valgus assembly218 out of their neutral positions. For example, in FIG. 36, thevarus-valgus assembly 218 is oriented to provide a lateral to medialslope if applied to a patient's left knee.

The movement of the posterior slope assembly 216 and the varus-valgusassembly 218 can be controlled by suitable mechanisms, such as forexample those illustrated in FIG. 38 and described above. The tibial jigassembly 212 can also be locked in any of a range of varus-valgus and/orposterior/anterior positions, such as for example by the cam- lockingdevices illustrated in FIG. 38.

As described above, the surgical orientation device 14 and referencesensor device 16 can be attached to the tibial jig assembly 212.Preferably, the surgical orientation device 14 can be locked in placerelative the tibial jig assembly 212. For example, referring to FIG.40B, the orientation device interface 230 can include a release device288 for releasably holding the orientation device 14 on the tibial jigassembly 212. The release device 288 can include an actuating member290, and a device 292 for applying a force to the surgical orientationdevice 14 (e.g. a clamp). The release device 288 can further comprise amounting bracket 294, a saddle 296, and saddle pins 298. In onearrangement, at least one of the surgical orientation device 14 and thereference sensor device 16 can be releasably attached to the tibial jigassembly 212.

In one arrangement, the release device 288 can also be used to actuate alocking device 299 disposed at a proximal end of the tibial assembly212. The locking device 299 includes a push button 299A that isslideably received in a channel 299B extending posteriorly from ananterior surface of the posterior slope assembly 216. See FIG. 40A. Thepush button 299A can be coupled with a gripping device disposed insidethe posterior slope assembly 216 that can be biased into grippingengagement with a portion of the cutting block assembly 224 (or otherremovable component) inserted into the posterior slope assembly 216. Bydepressing the push button 299A, the grip can be released from theportion of the cutting block assembly 224 inserted into the posteriorslope assembly 216. In one arrangement, the release device 288 has aproximally extending projection 292A for actuating the push button 299A.These features are discussed below in greater detail in connection withFIGS. 44A-B and 47-48.

FIGS. 50A-50B show a tibial jig assembly 212A that includes a tibialplateau mounting arrangement. The assembly 212A is similar to the tibialjig assembly 212 except as discussed below. The assembly 212A includes amounting bar 268A and a tibial plateau anchor 226A that is adapted toengage with the tibial plateau in a manner that secures the proximal endof the jig assembly 212A to the tibia. This arrangement eliminates theneed to secure the bone rest 276 to the tibia and can facilitateeliminating the bone rest completely. Also, this arrangement permitsgreater adjustability in the proximal-distal directions compared to theembodiment illustrated in FIG. 50, which shows the bone rest 276disposed distally of the position of the cutting block 332. The degreeof distal adjustment of the cutting block 332 is limited in that thebottom surface of the cutting block 332 would eventually contact the topsurface of the bone rest 276 is sufficient distal adjustment is made. Inthe embodiment of FIGS. 50A-50B, the bone rest 276 is not present andthus does not limit the proximal-distal adjustment.

The tibial plateau anchor 226A includes an anchor pin 226B, an arm 226Cthat can extend anteriorly of the anchor pin 226B, and a locking device226D that can be releasably secured to the proximal end of the mountingbar 268A. The anchor pin 226B can take any suitable configuration butpreferably includes a rigid pin that extends in a distal-proximaldirection when the jig assembly 212A is in use. The free (distal) end ofthe anchor pin 226B can include teeth that engage with the tibialplateau. In one technique the distal end of the anchor pin 226B isembedded in the tibial plateau by an amount sufficient to stabilize thetibial jig assembly 212A. In another embodiment, the arm 226C is securedto the tibial plateau by two screws (not shown) that are drive throughthrough-holes H that extend proximal to distal through posterior end ofthe arm 226C. Preferably the through-holes H include at least twothrough-holes H that are angled relative to each other so that the arm226C cannot slide proximally off of the screws.

An end of the arm 226C opposite the through-holes H extends anteriorlyto an anterior location that would correspond to the position of themounting bar 268A, i.e., just in front of the anterior face of the tibiain use. The arm 226C can be slidably coupled with the locking device226D at a joint 226E. The joint 226E can be a ring having an innerperimeter matching the outer perimeter of the arm 226C. The arm 226C canhave other features that facilitate mounting to the tibia, such as thosedescribed in connection with the midline probe assembly 226.

The locking device 226D can take any suitable configuration, butpreferably is adapted to connect to the mounting bar 268A by a releasedevice 226F. The release device 226F includes a finger actuatable lever226G that has a hook 226H at a distal end and a toggle 226I at aproximal end. The hook 226H is adapted to be received in a recess formedin the proximal end of the mounting bar 268A. The locking device 226Dcan also include a plurality of pins 226J that can be received incorresponding recesses 226K in the proximal end of the mounting bar268A.

FIG. 50B shows that in use, the jig assembly 212A can be secured to thetibia with screws, as discussed above, or by contacting or embedding thepin 226B in the tibial plateau and resting the mounting bar 266 and thelandmark acquisition device 214 on an anterior face of the leg.Thereafter the cutting block 332 (discussed below in connection withFIGS. 44A-B, can be positioned against the tibial section to beresected. As discussed above, with the bone rest not present, the degreeof proximal-distal adjustment of the cutting block 332 is enhanced.Prior to resecting the proximal tibia, the screws placed through thethrough-holes H could be removed if the resection plane is to beproximal of the distal end of the screws.

B. Orthopedic Assembly for Landmark Acquisition

FIGS. 41 and 42 illustrate various features of the landmark acquisitionassembly 214. The landmark acquisition assembly 214 can comprise astructure that is configured to contact and/or obtain information aboutanatomical landmarks on the human body. The landmark acquisitionassembly 214 can be attached to or form part of the tibial jig assembly212. For example, the landmark acquisition assembly 214 can bereleasably attached to the posterior slope assembly 216. The landmarkacquisition assembly 214 can comprise a distal tube assembly 300, aswell as a probe assembly 302.

The distal tube assembly 300 can comprise an elongate member 306, afirst clamping device 308 disposed at a proximal end of the elongatemember 306, and a second clamping device 310 located at the distal endof the elongate member 306. The first clamping device 308 can include acam member 314, and can be used to releasably fasten the distal tubeassembly 300 to the posterior slope assembly 216. The second clampingdevice 310 can include a knob 316 and slot 318. The knob 316 can be usedto tighten and/or adjust a position of a probe assembly positionedwithin the slot 318.

Referring to FIG. 42, the probe assembly 302 can include an elongatemember 320. The elongate member 320 can have a first portion 322 and asecond portion 324. In some embodiments, the first and second portions322, 324 are an angled relative to each other. In other embodiments, theelongate member 320 can generally be straight. The probe assembly 302can comprise a probe member 326 that is located on at least one end ofthe elongate member 320. The probe member 326 can be configured tocontact an anatomical landmark, such as for example a malleolus on apatient's ankle. The elongate member 320 can further comprise a seriesof markings 327, indicating distance and/or length. The markings can beused to measure, for example, an AP offset of the probe member 326.

C. Resection Guide for Resecting an Anatomical Feature

FIG. 43 illustrates various features of a stylus resection guide 222 forresecting an anatomical feature. The resection guide 222 can comprise apost 328 that can be received in a mount recess on a proximal aspect ofthe tibial jig assembly 212 (not shown). The stylus resection guide 222can further include a locking device 329, such as a detent mechanismcomponent, disposed thereon. The detent mechanism can be configured toengage a corresponding feature in the tibial jig assembly 212 toselectively mount the stylus resection guide 222 to the tibial jigassembly 212.

D. Cutting Block Assembly for Resecting an Anatomical Structure

FIGS. 44A and 44B illustrate various features of a cutting blockassembly 224 for resecting an anatomical structure. The cutting blockassembly 224 illustrated in FIGS. 44A and 44B is a left cutting blockassembly 224. The cutting block assembly 224 can be optimized, forexample, for resecting the proximal tibia of the left leg of thepatient. The cutting block assembly 224 preferably can be configured tobe moveable from a first position spaced away from an anterior surfaceof the tibia to a second position up against the tibia (e.g. as seen inFIGS. 48 and 49). A right cutting block assembly 224 can be formed as amirror image of the left cutting block assembly 224.

The cutting block assembly 224 can comprise an adjustment mechanism 330for distal-proximal adjustment of a cutting block 332. For example, theadjustment mechanism 330 can include a fastening device 334. Thefastening device 334 can comprise, for example, a threaded rod or othertype member that permits rotational movement of the adjustment mechanism330. The fastening device 334 can be inserted into a recess 299C (seeFIG. 46) that extends distally from a proximal surface of the tibialassembly 212. Thereafter, a gripping device coupled with the push button299A can be urged into frictional or teeth-to-teeth engagement withinthe recess 299C. The proximal-distal position of the cutting block 332can be adjusted by raising the actuating member 290 to cause theprojection 292A to depress the button 299A to release the grippingdevice from the threaded rod or other fastening device 334. Once thedesired proximal-distal position is achieved, the actuating member 290can be released to permit the push button 299A to move anteriorly, whichpermits the gripping device to once again grip the threaded rod (seeFIGS. 48, 49).

In some embodiments, the fastening device 334 can be secured by a springloaded locking member that is actuated by the actuating member 290 asdiscussed above.

In one embodiment, the cutting block assembly 224 can include a cuttingblock 332 and a positioning device coupled with the cutting block 332.The positioning device can comprise a coupling member for connecting thecutting block assembly 224 to another portion of the tibial jig assembly212, a cantilevered member 333 and a fine adjustment device. Thecoupling member can be an elongate member such as a rod. In oneembodiment, cylindrical grooves can be formed along the length of thecoupling member for engagement with a locking member. In one embodiment,the fine adjustment device can include a slot 335 formed in thecantilevered member along which the cutting block 332 can be moved.Preferably the cutting block 332 can also be attached to thecantilevered member in a way that permits the cutting block 332 torotate about an axis extending perpendicular to the cantilevered member(e.g., about a vertical axis). See FIG. 44A.

The cantilevered member can be shaped to facilitate positioning thecutting block 332 around other features of a jig. For example, thelocking device 226D of the tibial jig assembly 212A can be positioneddirectly between the location where the rod of the fastening device 334is received in the posterior slope assembly 216 and the location wherethe cutting block 332 is desired to be positioned. The cantilever memberof the adjustment mechanism 330 can be curved to extend laterally ormedially around the locking device 226. See FIG. 50B. This enables thecenter of rotation to be positioned anterior of the locking device 226D..

E. Midline Probe Assembly

FIGS. 45A-C illustrate various features of the midline probe assembly226. The midline probe assembly 226 can be used for determining aresection depth and/or an A/P offset of the tibial assembly 212. Themidline probe assembly 226 can comprise, for example, mounting pins 336that can be received in corresponding recesses 338 (see FIG. 48) in aproximal aspect of the tibial jig assembly 212, for example on aproximal surface of the mount bar assembly 220. The midline probeassembly can further comprise a set of markings 340 for helping toidentify an A/P offset, along with an adjustable probe bar 337 and guidebar 339, the guide bar 339 having an opening for receiving the probe bar337.

VIII. Tibial Preparation Methods

Referring to FIGS. 46-50, the tibial preparation system 210 describedabove can be used to prepare the tibia for a total knee replacement.

FIG. 46 illustrates the tibial jig assembly 212 fully assembled with areference sensor device 16 coupled to the reference sensor deviceinterface 228 and with a surgical orientation device 14 coupled with theorientation device interface 230. Advantageously, and as describedabove, the reference sensor device 16 can enable the procedure toproceed without fixation of the leg being operated upon because thereference sensor device 16 can track the relative positions of the tibiaand the surgical orientation device 14.

The midline reference probe assembly 226 can be coupled with a proximalface of the mounting bar assembly 220 and can be positioned at anappropriate anatomical location at the proximal tibia, for example at apoint just posterior to the insertion of the anterior cruciate ligament(ACL), or at another suitable anatomical landmark. For example, a tip341 of the midline reference probe assembly 226 can be resting over theinsertion point of the anterior cruciate ligament in the knee, and/or asoft point on the top of the tibia commonly referred to as the A/P pointof the mechanical axis. This point is generally located along a tibialspine on top of the tibia, and marks the location of a point along themechanical axis of the leg. Indicia of distance on an upper surface ofthe midline reference probe assembly 226 (e.g. via markings 340) can benoted and a corresponding A/P offset position can be set in the landmarkacquisition assembly 214 (e.g. via markings 327 described above) SeeFIG. 46.

Referring to FIG. 47, the method can further comprise acquiringlandmarks to determine the location of the mechanical axis passingthrough the tibia. For example, landmarks can be acquired by engagingthe probe member 306 of probe assembly 302 first with a medialmalleolus, and then with the lateral malleolus (or vice versa). FIG. 47illustrates acquisition of one malleolus. Acquisition of the othermalleolus can similarly be accomplished by swinging the distal tubeassembly 300 and a portion or portions of the tibial jig assembly 212such that the probe member 306 contacts the other side of the leg.Thereafter, the surgical orientation device 14 can determine thelocation of the mechanical axis, e.g., by locating sagittal and coronalplanes extending through the mechanical axis. In some embodiments, thesurgical orientation device can calculate the location of the mechanicalaxis by assuming that the mechanical axis extends from the point ofcontact of the midline reference probe assembly 226 with the proximaltibia through a point that is halfway between the two malleolus pointscontacted by the probe member 306 on either side of the leg, or anyother appropriate point.

In some embodiments, the user can activate the surgical orientationdevice 14, such as by pressing one of the user inputs 28 on the surgicalorientation device 14, during each landmark acquisition. Once activated,the, surgical orientation device 14 can register (e.g. record) theorientation of the surgical orientation device 14 as a referenceposition (e.g. a first reference position). For example, the surgicalorientation device 14 can register and/or calculate the currentorientation of the surgical orientation device 14 based on datacollected from the sensor(s) inside the surgical orientation device 14.The orientation of the surgical orientation device 14 in a firstreference position can be used to identify and register the orientationof a coronal plane which contains the mechanical axis of the leg, aswell as to determine a first reference point for identifying thelocation and/or orientation of a sagittal plane containing this samemechanical axis.

The user can then swing the probe member 306 over to the other (e.g.medial) side of the leg, such that the reference probe 306 is locatedadjacent the other malleolus. During each landmark acquisition, the usercan palpate the ankle. Once the location of the other (e.g. medial)malleolus is identified, the user can press one of the user inputs 28 onthe surgical orientation device 14 to cause the surgical orientationdevice 14 to determine the orientation of the surgical orientationdevice 14 in a second reference position. For example, the surgicalorientation device 14 can register and/or calculate the currentorientation of the surgical orientation device 14 based on datacollected from the sensor(s) inside the surgical orientation device 14.

The orientation of the surgical orientation device 14 in the secondreference position can again be used to identify the orientation of acoronal plane extending through the tibia that contains the mechanicalaxis of the leg, and/or can be used to locate a second reference pointfor identifying the location and/or orientation of a sagittal planecontaining the same mechanical axis.

When using the surgical orientation device 14 to determine the first andsecond reference positions, output of the sensor(s) in the surgicalorientation device 14 can be monitored in a manner that minimizes errorin the reading. For example, a transient phase can be eliminated in theoutput of the sensors to arrive at an accurate estimation of the givenanatomical landmark.

Once information about both the first and second reference positions hasbeen acquired and registered in the surgical orientation device 14, thesurgical orientation device 14 can determine (e.g. calculate) thelocation of a desired plane between the lateral malleolus and the medialmalleolus. The desired plane can correspond to the sagittal planecontaining the mechanical axis. The desired plane can vary, depending onfactors such as the patient's specific anatomy and the surgeon'straining and experience. For example, the desired plane can be locatedmidway between the lateral malleolus and medial malleolus, or 55% towardthe medial malleolus from the lateral malleolus, or at some otherpredetermined location.

The user can use one or more user inputs 28 to direct the surgicalorientation device 14 to calculate the location of and/or orientation ofthe sagittal plane. Once the surgical orientation device 14 hascalculated where the sagittal plane is, the surgical orientation device14 can provide location feedback to the user, for example in the form ofa visual signal or signals on the display 26, indicating that thelocation of the sagittal plane has been calculated.

In some embodiments a laser can be provided on the surgical orientationdevice 14 to confirm the position. The tibial assembly 212 can beconfigured to interact with the laser to provide a confirmation ofalignment. In one embodiment, the laser can emit a cross-hair laserpattern in which a first component is directed through slots and asecond component impinges on indicia on the probe member 306 distallyand/or on the midline reference probe assembly 226 proximally as aconfirmation of appropriate positioning of the midline reference probeassembly 226. Embodiments of laser use are described, for example, inU.S. Patent Publication No. 2010/0063508, the contents of which areincorporated by reference in their entirety.

Referring to FIG. 48, once the mechanical axis has been identified, themidline reference probe assembly 226 can be removed and replaced withthe tibial cutting block assembly 224. The cutting block assembly 224can be positioned such that the cutting block 332 is spaced away fromanterior surface of the tibia. The surgical orientation device 14, andtibial assembly 212, can be used to adjust the cutting block 332 inorder to obtain a desired orientation for resection of the top of thetibia.

For example, the posterior slope assembly 216 and varus/valgus assembly218 can each be independently adjusted to change the angle of thecutting block 332, and subsequently, the angle of the intendedresection. During this adjustment, the surgical orientation device 14can provide a reading or readings on its display 26 indicating whetherthe surgical orientation device 14 (and likewise the cutting block 332)is aligned with the sagittal plane and/or coronal plane containing themechanical axis.

Referring to FIG. 49, the method can further comprise rotating thecutting block 332 such that the cutting block 332 is positioned upagainst an anterior surface of the proximal tibia once the desired anglehas been set.

Referring to FIG. 50, once the cutting block is in position, the cuttingblock 332 can be mounted to an anterior surface of a proximal portion ofthe tibia by a plurality of pins 342. The surgical orientation device 14can be removed, as can the tibial assembly 212. After the cutting block332 has been mounted to the tibia, a proximal portion of the tibia canbe resected.

IX. User Interfaces for Tibial Preparation Methods

As discussed above, in at least one embodiment, the surgical orientationdevice 14 can display on-screen graphics or GUI images for communicatinginformation to a user based on input commands and orientation data. Theimages can be instructive for performing a joint replacement surgery.

FIGS. 51A-51L display exemplary screen shots that can be displayed bythe interactive user interface of the surgical orientation device 14(e.g. displayed on an LCD screen on the front of the surgicalorientation device 14) during the various steps of an orthopedic method.

For example, FIG. 51A displays a screen shot that provides a visual cueinforming the user to check the surgical orientation device 14 andreference sensor device 16 to see if batteries are installed, and tocheck to make sure the surgical orientation device 14 is detecting thereference sensor device 16.

FIG. 51B displays a screen shot that provides a visual cue informing theuser to confirm whether a green LED light is lit on the reference sensordevice. If there is a green light, the surgical orientation device 14has detected the reference sensor device 16. The image in FIG. 51B canbe displayed in response to pressing a user input button 28 specified bythe surgical orientation device 14 in FIG. 51A.

FIG. 51C displays a screen shot that provides a visual cue informing theuser to acquire and confirm a neutral position of the surgicalorientation device 14. For example, the user can place the surgicalorientation device 14 on a level surface with its display screen 26facing up, and the user can confirm whether there is a 0 degree readingfor both varus/valgus and posterior slope. The image in FIG. 51C can bedisplayed in response to pressing a user input 28 button specified bythe surgical orientation device 14 in FIG. 51B.

FIG. 51D displays a screen shot that provides a visual cue informing theuser to select the right or left knee. The image in FIG. 51D can bedisplayed in response to pressing a user input 28 button specified bythe surgical orientation device 14 in FIG. 51C.

FIG. 51E displays a screen shot that provides a visual cue informing theuser to place the tibial assembly 212 against the tibia, to secure thereference sensor device 16 to the tibial assembly 212, and to secure themounting bar assembly 220 to the tibia, for example with pins. The imagein FIG. 51E can be displayed in response to pressing a user input 28button specified by the surgical orientation device 14 in FIG. 51D.

FIG. 51F displays a screen shot that provides a visual cue informing theuser to confirm that the tibial assembly 212 is in a neutral position.The image in FIG. 51F can be displayed in response to pressing a userinput 28 button specified by the surgical orientation device 14 in FIG.51E.

FIG. 51G displays a screen shot that provides a visual cue informing theuser to confirm movement capabilities of the swing arms (e.g. movementof posterior slope assembly 216 and varus/valgus assembly 218). In someembodiments, the user can confirm maximum ranges of angular adjustment.The image in FIG. 51G can be displayed in response to pressing a userinput 28 button specified by the surgical orientation device 14 in FIG.51F.

FIG. 51H displays a screen shot that provides a visual cue informing theuser to confirm an A/P offset based on markings on the midline probeassembly 226 and landmark acquisition assembly 214. The image in FIG.51H can be displayed in response to pressing a user input 28 buttonspecified by the surgical orientation device 14 in FIG. 51G.

FIG. 51I displays a screen shot that provides a visual cue informing theuser to register a first landmark (e.g. malleolus). The image in FIG.51I can be displayed in response to pressing a user input 28 buttonspecified by the surgical orientation device 14 in FIG. 51H.

FIG. 51J displays a screen shot that provides a visual cue informing theuser to register a second landmark. The image in FIG. 51J can bedisplayed in response to pressing a user input 28 button specified bythe surgical orientation device 14 in FIG. 51I.

FIG. 51K displays a screen shot that provides a visual cue informing theuser to determine a desired anterior/posterior slope angle andvarus/valgus slope angle for resection. The image in FIG. 51K can bedisplayed in response to pressing a user input 28 button specified bythe surgical orientation device 14 in FIG. 51J.

FIG. 51L displays a screen shot that provides a visual cue informing theuser to remove the midline probe assembly 212 and to set a resectiondepth using the stylus 222. The image in FIG. 51L can be displayed inresponse to pressing a user input 28 button specified by the surgicalorientation device 14 in FIG. 51K.

FIGS. 52-55 display additional exemplary screen shots that can bedisplayed by the interactive user interface of the surgical orientationdevice 14 (e.g. displayed on an LCD screen on the front of the surgicalorientation device 14) during the various steps of an orthopedicprocedure.

For example, FIG. 52 displays a screen shot that provides a visual cueinforming the user that a procedure is finished.

FIG. 53 displays a screen shot that provides a visual cue informing theuser that the surgical orientation device 14 has completed and passedone or more self-tests.

FIG. 54 displays a screen shot that provides a visual cue informing theuser that the surgical orientation device 14 is experiencing a systemfault.

FIG. 55 displays a screen shot that provides a visual cue informing theuser to confirm again whether the left or right leg is being prepared.This visual cue can appear, for example, if the user is registering thelateral malleolus and the tibial assembly 212 continues to move in alateral direction, as opposed to a medial direction.

Further embodiments of user interfaces, for use for example in anorthopedic method, can be found in paragraphs [0377]-[430] and FIGS.58A-61K of U.S. patent application Ser. No. 12/509,388, which isincorporated by reference herein.

X. Attachment of Prosthetic Components

Once all of the tibial and/or femoral cuts are made with the systemsand/or methods described above, a knee joint prosthetic or prostheticscan be attached to the distal femur and/or proximal tibia. The kneejoint prosthetic devices can comprise a replacement knee joint. Thereplacement knee joint can be evaluated by the user to verify thatalignment of the prosthetic components in the replacement knee jointdoes not create any undesired wear, interference, and/or damage to thepatient's anatomy, or to the prosthetic components themselves.

While the systems and methods presented herein are described in thecontext of a knee joint replacement procedure, the systems and/or theircomponents and methods can similarly be used in other types of medicalprocedures, including but not limited to shoulder and hip replacementprocedures.

Additionally, while the systems and methods presented herein aredescribed in the context of individual components and assemblies, insome embodiments one or more of the assemblies can be provided in theform of a kit for use by a surgeon. For example, in some embodiments akit can comprise each of the components of the femoral preparationsystem 10 and the tibial preparation system 210 described above. In someembodiments, a kit may comprise only the surgical orientation device 14and reference sensor device 16. In some embodiments a kit may compriseonly the femoral preparation system 10, or only the tibial preparationsystem 210. Various other combinations and kits are also possible.

Although these inventions have been disclosed in the context of certainpreferred embodiments and examples, it will be understood by thoseskilled in the art that the present inventions extend beyond thespecifically disclosed embodiments to other alternative embodimentsand/or uses of the inventions and obvious modifications and equivalentsthereof. In addition, while several variations of the inventions havebeen shown and described in detail, other modifications, which arewithin the scope of these inventions, will be readily apparent to thoseof skill in the art based upon this disclosure. It is also contemplatedthat various combinations or sub-combinations of the specific featuresand aspects of the embodiments can be made and still fall within thescope of the inventions. It should be understood that various featuresand aspects of the disclosed embodiments can be combined with orsubstituted for one another in order to form varying modes of thedisclosed inventions. Thus, it is intended that the scope of at leastsome of the present inventions herein disclosed should not be limited bythe particular disclosed embodiments described above.

1-9 (canceled)
 10. A system for orthopedic surgery, comprising: anorthopedic fixture configured to couple to a bone of a patient, whereinthe orthopedic fixture comprises a first interface and a secondinterface, a first orientation device configured to couple to the firstinterface, wherein the first orientation device comprises one or moresensors configured to sense changes in acceleration and/or gyroscopicpositioning; a second orientation device configured to couple the secondinterface, wherein the second orientation device comprises one or moresensors configured to sense changes in acceleration and/or gyroscopicpositioning; and wherein at least one of the first orientation deviceand the second orientation device is configured to communicate changesin acceleration and/or gyroscopic positioning of the at least one of thefirst orientation device and the second orientation device to the otherof the first orientation device and the second orientation device. 11.The system of claim 10, wherein at least one of the first orientationdevice and the second orientation device is configured to locate aportion of a mechanical axis.
 12. The system of claim 10, wherein atleast one of the first orientation device and the second orientationdevice is configured to calculate a center of rotation.
 13. The systemof claim 10, wherein at least a first portion of the orthopedic fixturecomprising the first interface is configured to be fixed relative to thebone.
 14. The system of claim 10, wherein at least a second portion ofthe orthopedic fixture comprising the second interface is capable ofmovement relative to the bone.
 15. The system of claim 10, wherein atleast one of the first orientation device and the second orientationdevice comprises at least one structure for facilitating releasableattachment to the orthopedic fixture.
 16. The system of claim 10,wherein a display is visible to a user when the first orientation deviceand the second orientation device are coupled to the orthopedic fixture.17. A system for orthopedic surgery, comprising: an orthopedic fixturecomprises a first interface and a second interface, wherein the secondinterface is movable relative to the first interface; a firstorientation device configured to couple to the first interface, whereinthe first orientation device is configured to sense changes relative toone or more reference points, lines, planes, and/or gravitational zero;a second orientation device configured to couple the second interface,wherein the second orientation device is configured to sense changesrelative to one or more reference points, lines, planes, and/orgravitational zero; and wherein at least one of the first orientationdevice and the second orientation device is configured to communicatechanges relative to one or more reference points, lines, planes, and/orgravitational zero of the at least one of the first orientation deviceand the second orientation device to the other of the first orientationdevice and the second orientation device.
 18. The system of claim 17,wherein at least one of the first orientation device and the secondorientation device comprises a display.
 19. The system of claim 17,wherein at least one of the first orientation device and the secondorientation device is configured to calculate a point on a mechanicalaxis.
 20. The system of claim 17, further comprising a probe forreferencing a point.
 21. The system of claim 17, wherein the firstinterface is configured to enable low profile mounting of the firstorientation device.
 22. The system of claim 17, wherein a cutting guideis configured to couple to the orthopedic fixture.
 23. A system fororthopedic surgery, comprising: an orthopedic fixture configured tocouple to a bone of a patient, wherein the orthopedic fixture comprisesa first interface and a second interface, a first orientation deviceconfigured to couple to the first interface, wherein the firstorientation device is configured sense angular changes of the firstorientation device; a second orientation device configured to couple tothe second interface, wherein the second orientation device isconfigured sense angular changes of the second orientation device;wherein at least one of the first orientation device and the secondorientation device is configured to communicate angular changes of theat least one of the first orientation device and the second orientationdevice to the other of the first orientation device and the secondorientation device.
 24. The system of claim 23, further comprising adisplay configured facilitate orienting a cutting guide relative to amechanical axis.
 25. The system of claim 23, further comprising adisplay configured to indicate angular displacement in ananterior-posterior plane
 26. The system of claim 23, further comprisinga display configured to indicate angular displacement in amedial-lateral plane.
 27. The method of claim 23, wherein at least oneof the first orientation device and the second orientation devicecomprises an inertial sensor.
 28. The system of claim 23, furthercomprising a landmark contacting probe.
 29. The system of claim 23,wherein at least one of the first orientation device and the secondorientation device is configured to calculate a point on a mechanicalaxis.